The biggest difference between any two players is their relative experience with the position on the board between them. There are only two ways to tip that balance in your favor: 1. Play more chess than your opponents in every position youíre likely to meet 2. Lure your opponents into positions youíve played more often than they have. For this you need a opening repertoire that you can use to play these positions over and over again that will give you that experience. But no matter which horse you decide to ride, youíre going to be thrown again and again. Just get back on again and again and donít ever give up. The harder that horse is to ride, the better will be that experience for you.
See How to learn the basics
There are other considerations to improve your chances that may not involve any study what so ever. Just common sense ideas that may help to give you an advantage.
Choose your opening or defense carefully.
If your opponent is rated higher than you, then his overall chess knowledge of openings and defense is probably better also. Maybe you think it would be a good idea to surprise him with a weird unorthodox variation? Why do you think that these unorthodox variations are so unconventional and rarely used? The reason he may not know much about this variation is probably because it is a variation that good players have found to be inferior and give little chances of success. How many of these unorthodox, weird, contentious, controversial, unconventional arrogant and outright strange openings with many bizarre names do you ever see Grandmasters play? Just think about it, if any of them were any good the GM's would be using them, right? The best openings and defenses to use are the ones that you have studied. It is far better to study and thoroughly learn just a very few of the best classical most often used ones than to try to have a opening repertoire of unorthodox openings that most chess players rarely use. If you spend time with just a few of the most common ones, the chances are that you may be more familiar with the ideas and principles behind that opening than he does. It is far better to excel at just a few openings than to be mediocre at all.
Trying traps and swindles.
While you are playing you see some combination of moves that will give you a great advantage, if your opponent does not see it, but if he does, his refutation will put you at a great disadvantage. Do you play it? What makes you think that if you were able to find this combination at your level of play that he did not see it long before you did? Or may be he just maneuvered you into that position setting you up in a trap to zap you. Don't fall for this kind of swindle, and be very careful about setting up one. It's best to always assume that if you quickly found the refutation so will your opponent. If you can set up a trap or swindle in such a way that if it fails you have not jeopardized your position, then it can be tried safely.
Keeping your cool.
If your game starts to drastically turn for the worst don't give up. There is no guarantee that your opponent will not make a blunder or stupid mistake that will change your play and the outcome. He may become complacent and think he has a easy won game letting his guard down for you to make a combination that ordinarily he would never let you do. You can also think of this as a golden opportunity as a lesson in how to improve your play. There are many that just get disgusted and try to end the game as quickly as possible. Some people get so down that they just can't play any more and disconnect and quit. Their egos just can't take defeat. They just can't see any benefits from losing their games. They are just too shortsighted to see that playing strong players is going to teach them how to play better and improve their chess skills. You might think of it as getting free lessons and advice that others pay for. If you constantly play stronger players than you, then you will soon get use to managing your psychological fears of losing. This could be a great advantage against a stronger player that has trouble doing this. If you can create some tension in your play and maintain that tensions for him long enough, he just may crack under the pressure and make the blunder that lets you win the game. Just remember about the tortoise and the hare.
Try to play at your best style of play.
There are not many chess players that play equally well in all areas of chess. Everyone is better at some type of play than at others. If you find that you can play very well in the endgame then that is what you should try to be the best at. If you have a good memory and are good at remembering many different opening variations then you could try to get into deep opening preparation. Tactics, strategy, attacking play, positional play, solid defensive play, pawn play knowledge, pawn structure, etc, etc. You don't have to thoroughly study everything to be better than your opponent. The best way to defeat your opponent is by outplaying him at your best style of play and utilizing your strengths. A good strategy is to get him to veer away from his best style of play if you can and then capitalize on your strengths. Most strong players have three times as much trouble in defending than at attacking play. So you will do well if you study up on your attacking play and make the difficulty of your opponent so great in his defensives that he makes serious errors in his play. Of course if stronger players have so much trouble in their defensive play you can expect to be even worst in yours. So it is obvious that you can't expect to do better in defensive play than him if you don't study defensive play also. Sorry, I never said it was going to be easy to defeat a stronger player than you.
Maintaining the edge as White
When you get white you have the advantage of being able to immediately challenge control over the center. This small edge gives you the opportunity to quickly develop your pieces and get a central superiority. Don' t lose this advantage by choosing a bad variation that you may think will throw him off. Always stay with the sensible proven variations that you know will give you fighting chances. Try to steer into variations that you have studied to give you the edge. Be satisfied with what strong players are satisfied with. Even a slight noticeable edge at the start of the opening to build on may lead to an excellent positional advantage in the middlegame.
How to play as Black
Its true that black loses about 57% of his games but it also means that he won 43% of the time to. Try to stay out of a variation that is so passives that you have to play perfectly just to squeeze out a draw. Trying to defend against a stronger player than you that will require many moves of careful defending is just playing into his hands. He knows how to increase the pressure and you will blunder sooner or later. His superior knowledge will allow him to gain the edge as soon as your position offers up a imbalance in his favor. The best approach is to play a good sound variation where there are good opportunities for attacking counterplay. In this type of play he will not be making you play as the defender all the time. He will have to watch out for you seeing an opportunity to gain a attacking position that may affect his judgment to err in your favor. He no longer plays in his familiar backyard. Getting him out in unfamiliar territory gives you the chance for seeing a combination or a sacrifice that will change the game over in your favor that you may never get if you were defending.
How to keep an advantage
Whenever your play moves to a definite advantage or a won position your next step is actually using it to win the game. A stronger player may have problems with the first part but usually the second part goes smoothly. It is the weaker player that has problems with the second part. The major problem is that the weaker player treats both parts in the same way. In the first part often a substantial amount of risk must be tolerated. A sacrifice of material, serious comprises in some position or the development of your pieces in an area of the board is neglected. A trade off was made to obtain superior compensation for this advantage. At this point it is immaterial how you got your superior position. Once you have it you need to play very carefully not to lose it. The rule is to now to avoid any kind of risky play that may jeopardize it. This is absolutely mandatory whenever you are playing against a superior opponent. How this is done is by following the same basic rules and principles that are put to use in the end game. When you are ahead in material continually try to simplify the game by exchanging pieces. Maintain your material advantage. Avoid any unclear or unnecessary complications. Stay away from any counterplay. As an example if you have a passed pawn heading for a clear shot to be a queen, don't get complacent and start an attack on his king. You might get your king in a perpetual check and wind up in a drawn game, or worst actually lose the game. Establish and stick to a clear plan.
You may have the advantage in the middlegame.
Your superior opponent will be superior in knowledge, experience and tactics. Expect less than 38% of errors to come from his tactics. His knowledge of the openings are better to and less than 19% of his openings are going to be responsible for a loss. He is even better in the end game where you can expect less than 16% of his games to lose from end game errors. But two-thirds or about 65% of his loses come in the middle game. This is where you opponent is most vulnerable. It is in the middle game where deep strategic concepts, creativity and original thought assume the greatest importance, whereas general technical knowledge and experience diminish in importance. It is in the middlegame that the less experienced player has a better chance to compete. The substantial majority of losses occur because of making strategic misjudgments in the middlegame. When the strategic requirements of a position are not obvious, more than one approach may seem to make sense, but it is very difficult to decide which approach is the right one. Therefore, errors of judgment can occur very easily. If you can create a position where the solution is of a strategic nature, rather than tactical, your opponent no longer has the advantage of more knowledge or more experience to help him. He now has to solve a brand new problem, and the chances are good that he will not be able to solve it most of the time under the practical consideration of the clock. Time pressure may change his ability to cope with the strategic needs of his position. Even very strong grandmasters have problems doing this. So you can expect your opponent to be sure to have an even more difficult time under similar circumstances.
Use an advantage in the middlegame for a successful endgame.
Do not expect to have many successes against a higher-rated player in the endgame. So do not enter into an endgame unless a draw is obvious. When you have the choice between a full play middlegame and a full play endgame, choose the former. Even worst is for you to voluntarily enter into an inferior endgame from a inferior middlegame. If you have gained a significant advantage from the opening or middlegame, try to avoid losing it and keep that advantage for winning chances in the endgame where you do not play as well as your stronger opponent.
Don't play to win hoping for a blunder or error in your opponent's play.
During any game there may be a lot of nervous tension that makes errors inevitable. This holds true for all chess players from Grandmasters on down. The major difference between the top players and those lessors ones is not that the top players don't make errors and blunders, but their attitude towards making them. They expect to make them and they expect their opponents to make them as well. But the top players expect to make less of them and they expect that their errors will not be as serious as the lessor player. If you find that your opponent has made a blunder don't get complacent and get a false sense of optimism which can let your guard down. Your opponent knows that if his error or bad blunder did not result in a checkmate or immediate lost game that the chances are good that soon you will make a error or blunder that was even worst than his, and then it may be all over. However if you think that the game is really going badly for you don't give up. Blunders can occurs at anytime in the game. As long as you are still in the game errors may occur enough times to make a difference in the final outcome of the game. This hope is a valid reason for making a good fight to succeed. Never get despondent if your error has placed you in a very poor position. Just remember that you are playing with a human that can be affected by the same factors that affect you. Every one does not play at the same level of expertise every day. Some days are better than others are and some days you think you just should have stayed in bed. If your opponent is having a bad day, it is not cheating to take advantage of his misfortune. You may notice that he is having trouble staying focused on the game and if you can keep up your resistance and keep up the tension in a game for a long period he just may crack under the pressure and make a big enough blunder that he gets so despondent that he just wants to end the game as quickly as possible.
Watch out for Time Pressure.
Time pressure can cause even the best of players to have trouble keeping the mind functioning well. So if the top players have trouble with time pressure, your play will be even worst. Your chances of coping with time pressure when facing a strong opponent through out the game are next to zero. To avoid this time pressure dragon you must get in the habit of always saving time. You must learn to budget your time just as you budget your money. You must know in advance what kind of opening your going to play if you are White and how to play it before you start the game with a strong opponent. If your black you must know exactly what kind of defense you will play against his opening moves. Save time by playing obvious moves and routine recaptures quickly. If you see a variation that looks good to you and you've checked it through twice, go for it. Don't procrastinate. If two moves look both equally good play one of them quickly. If you play quickly in the beginning of the game you will have more time latter in the game for the tougher decisions. Also if you can gain a lot more time than your opponent, this may be a psychology plus for you against him You may create a time pressure block for him to play against. Go to the bathroom before the game starts. Make sure you are not thinking about eating. Low blood sugar can effect your thinking also.
Check out your opponent.
Unlike OTB tournament play, on the Internet you may choose your opponent. One way to help give you the edge is to do like the Grandmasters do. They first study the games of the opponent that they are going to play. There is no reason that you could not do the same by examining the games in that opponent's history. You could find out much there. His opening preference, his style of play, what areas of chess he is strong and what areas he needs a lot of improvement in. If this was done in OTB tournament play I'm sure that the game would take on a totally different type of play and the ratings would be a lot different than they are now. This is one reason that it is very hard to make a comparison of a internet rating to ELO or USCF ratings.