grand theft auto iii features non-linear gameplay, meaning you are usually free to do whatever you like and don't have to play the main missions. There are some distractions you can focus on instead, but the most fun is to be had by following the game's set storyline.
Your current objective is displayed on the game's minimap, allowing you to find it while driving more easily. missions earn you money, which you can then use to purchase weapons and armor to help for your life of crime.
You can get in any of the vehicles you see on the street, though be aware that stealing one will attract the attention of the police, should they catch you in the act. Once the police are onto you, you are assigned a star rating, going up to five. Each star means more and more police come after you (eventually including the army), as the severity of your crimes increase. Generally, once you've killed a police officer, things tend to get pretty serious!
There is a lot to do in the game, and this guide will aim to help you achieve 100% completion and find all of the easter eggs and secrets on offer.