The easiest way to ensure victory in GTA Vice City online is to use the infinite ammunition unlock. It is simple to do and only requires pressing the controller buttons in the following sequence: R1, R2, L1, L2, Down, Up, Down and Up.
While many might say that using the infinite ammo unlock is unfair, those people should remember that the name of the game is Grand Theft Auto. The premise of the game is that the protagonist is a criminal struggling through the ranks of organized crime. This game is not intended for individuals who have high game play principles. To play through the story mode with unlimited ammunition could be considered as a "cheap" or boring way to play, but when it comes to online game play, unlimited ammo is king.
Another great tip for winning during a car battle is to use the brakes. Braking while involved in a high speed chase catches an opponent off guard and gives a player the upper hand. When being chased, a player can use his vehicle as a weapon if he has time stop and get out. This makes the player doing the chasing crash into the empty vehicle. Players can ditch the car while driving, but that often will not leave the car parked. Also, stopping while in pursuit can often help a player aim his weapon to get a head shot through the rear window.