Instructions
Find a decent car to pick up people who populate the grand world of Liberty City. In order to get a nice set of wheels, the quickest way is to steal one. To do so, approach a vehicle with a driver and others inside when it makes a complete stop. Pull the driver and hop onto the vehicle and you have friends on your joyride.
Locate a taxi no matter if it is empty or with the driver cruising the streets. Steal the taxi and press the R3 button to activate the Taxi mission where you go from locale to locale picking up passengers. This makes a good way to earn cash in Liberty City to finance your exploits.
Prostitues litter the streets as much as the trash so find a street walker on a corner waiting for her next john. Drive up and honk your horn to signal her to come over to your car and she'll ask if you want company. Answer "yes" and you'll have one passenger who aims to please (of course it will cost you).
Online play features places where other players can recruit others when playing the multiplayer modes offered---from deathmatches to mafia work. Drive over to a group of fellow gangsters, honk your horn to welcome them to your car and head out to carnage and fun against other gangs.