There are times as a gamer where you will find yourself in a multiplayer match against the person who owns the game that you don't and in those cases you are not expected to win as you don't own the game yourself, but here are a few tips that just might give you an edge.
GeneralIf you are playing split screen looking at your opponents view can sometimes give you an advantage by letting you know where they are, what weapons or powerups they have and possibly what their intentions are (i.e a cover battle in Perfect Dark Zero).
FPSUse sound to your advantage. If you hear footsteps from your right speaker then it is likely there is somebody off to your right. Being able to locate people in a level by sound alone is an excellent radar substitute.
When running around corners make sure you are looking towards the apex of the corner. This will allow you to see anybody who is waiting for you just inside.
If you have a weapon that is slow reloading make sure you have auto-reload turned off in the options. That way when it is empty instead of dodging fire while it reloads, switch weapon. This also had the added advantage by putting intermediate opponents offguard as they will think you are reloading and unable to fire.
Mouse sensitivity should be set on a game per game basis depending on they types of weapons used. A high sensitivity will help with twitch action and following fast moving targets where as low sensitivity will give much better accuracy when firing and both moving and stationary targets, so is essential when sniping.
StrategyMost strategy games have a fundamental flaw in that the amount of technology, buildings and units is dictated by how much resources the player has. Has soon as the match starts make sure you secure most of the resources on the level. If you are playing against newbs get the resources in the middle of the level first and then the ones closes to your base. Otherwise you will have a small firefight to get the resources in the middle of the level with more experienced players.
Don't spend all your time on defence and technologies. These are generally a wast of time. Your objective should be to win as fast as possible because most players will sitback and build until they are ready to attack.
2D beat-em-upsButton mash, nothing can help you here.
3D beat-em-upsChoose a fast character, these are generally balanced so that their weaker attacks aren't much weaker than their powerful attacks, which you aren't going to use because you don't know them. Plus having a faster character will make it easier to dodge attacks.
Learn your opponents moves to know when to block and when to sidestep. Your objective should be to reduce the amount of health you loose, over the priority of dealing damage to them.
RacingGo slow into corners and fast out. This will take advantage of the simulated weight distribution of the car by having the weight on your front tires when you are breaking and the car's weight on your back tires when accelerating. And yes most racing games simulate this. The only game which probably doesn't is Mario Kart.
Front wheel drive cars are always easier to steer and wipeout less.
MechbattlesConcentrate fire on a specific part of your opponent and make good use of splashdamage. The unfortunate thing here is that experience is really everything.
Games with powerupsIn some of these games grabbing the powerups is good, in others it is not worth the effort. Know witch of these types of games you are playing.