Whether it is a realistic driving simulator like Gran Turismo, a rally course time to beat or a shell throwing game (you know the one that I am referring to), there are several tactics which could put you a place better than them by following these handy pointers:
Drive towards the outside of a track when on a straight line, and then when approaching a corner, slowly drive inside the curb of the corner and then exit the corner by going back on the outside as you entered it first. This is known as the ideal racing line for a corner, particularly for realistic racing games.
At times your friends may have an item or power up which can be anything which will make you slow. Projectiles such as rockets or flying shells are an example here. With reference to cute kart racing games such as Mario Kart or Crash Team Racing, if you are ahead of a friend who has a projectile weapon and is about to fire at you, always be sure to have some form of defence. In some games, you are able to fire projectiles behind you, so as a rocket is approaching you, fire away behind and with perfect timing, it should detonate the oncoming projectile, making you safe for the time being!
If you want to be the best, there are tactics which although are discreet, are not very sportsman like but can provide you with a competitive edge over your mates. One tactic can be known as barging friends who are close to you, so you can put them off their racing line and eventually forcing them to manoeuvre away from you. In cute carting games, a heavier character is an ideal example of this when you can push away the smaller racers, possibly even off the track entirely when they fall into boiling hot lava (cue evil laughter here).
Finally a tip for the ones always ending up playing catch up, although you are behind the leader/s, the trick is to persevere and keep at them. Eventually you may even come to a point where the distance between you and the leader becomes so small that it will put a lot more pressure on them, making them about 30% more prone to committing an accident!