By using the ''Jumping Cars'' trick, you can access other parts of the city you can't in the beginning of the game, from the broken down bridges. Just go to the bridge you want to cross, and use the ''Jumping Cars'' trick when your just about to hit the edge of the bridge. You will then cross the bridge safely (might take a try or two), and be able to try out some new city life!
When you're doing the mission on Staunton Island for Ray Machowski called ''Gone Fishing'', you're supposed to kill the guy on the boat. If you stand on the shore with your sniper rifle and shoot him as he goes by, he may turn the wrong direction and beach himself.
If you shoot him as he's standing on the shore, the boat remains. Press the Triangle button as you would to get into any other boat, and press the Square button like you're reversing. The boat won't go too far, but if you keep holding the Square button down, eventually you can get back into the water, assuming the boat doesn't flip.
The boat handles REALLY well, goes pretty fast, and goes by the title of ''GHOST Missing''. If you dock it and shoot it to make it explode, it does explode, but it still remains as though it's new. You can't really see yourself inside the boat, as it was never meant for you to drive anyways.
Little thing, but it's fun.
Enter the full health cheat (R2, R2, L1, R1, Left, Down, Right, Up, Left, Down, Right, Up) while in a vehicle and that vehicle's damage will be repaired. The visual damage will remain but the vehicle's condition will be as if it were new.
On the second island (Staunton Island), go to the left of the main entrance of the car park that was used in the Kingdom Come mission. Go up the stairway you find up the alleyway with a car and park the car by the wall to the right. The wall is too high to jump on so you will need the car. Jump on the car, then on the wall and you will be on a flat roof. Jump off the wall to the area where you see all the metal fire escape stairways and look around. You will then see a message on one of the walls that reads: “You werent supposed to be able get here you know”.
Get a normal car and cruise the streets until you find a hooker drive up next to her (make sure she is standing next to the drivers door) and she will talk to you for a couple of minutes then she will walk around to the other side of the car and get in. Drive to a dark place (an alley, your hideout etc.) and park the car but do not get out. The car will start shaking and your health will go up. Then you have two choices:
1)Stay still and let her get out then beat her up to get your money back, or
2) tap the gas right before she gets out then park the car and watch the car start shaking again which saves time since it costs a dollar a second when she is in the car.
If you want to get to the third Island and haven't earned it, you can ''fall'' into the underground passage. You'll need the Car Handling Cheat entered (R1 L1 R2 L1 left R1 R1 Triangle) and an esperanto. You must have an Esperanto - it's the only car that will jump high enough. First, get to the hospital in Staunton Island. then, go to the parking lot and go as fast as you can towards the Hospital. Make sure that you are on the left side of it... It's hard to do it without doing that. Jump onto the platform above the Hospital ''Entrance'' and go slowly straight to the square-looking wall. Go into it turning right, and go forward. You should fall out of the world and land in the underground passage. Turn right and go quicly to the beauty of Shoreside Vale. If you hit a blue wall, turn around and go.
To exploit this glitch it's just a matter of putting the fire out as the clock is going to hit 0. If done correctly, the timer will disappear allowing infinite time to cruise to the next fire.
Whenever the moon is visible at night shoot it with the sniper rifle to make the moon bigger or smaller.
Go to any garage that can fit two or more cars in. When It is full, get another car right up next to the door, and get out. Press triangle as the door is going up, and hit X fast to get the car in. You might have to move the cars in the garage around, but it's possible to get up to 6 cars in any given garage.