1. turn on xbox 360 (make sure gta4 disc is in)
2. push and hold shiny X button on center of Xbox 360 controller
3. wait for gta 4 to load while listening to the cool loading music
4. once loaded, push "up" on the directional pad (not the joystick) this should bring up your cell phone
5. push "up" again, this should bring up the numbers
6. enter the cheat code by highlighting the correct number and pushing "a"
7. highlight the talk button. this is the little green phone
8. push "a"
9. acknowledge that the phone says "cheat code entered"
10. have fun
cheats may be found at
http://www.cheatcc.com/xbox360/grandtheftauto4cheatscodes.html
a very helpful resource map
http://grandtheftauto.ign.com/maps/1/Liberty-City-Map
tips-
if you want to lose stars fast, hop into the subway tunnel. an entrance is found at the intersection of uranium and frankfort ave, just north northwest of middle park, on Algonquin island (the middle island). you can use the map above to pinpoint the location. you can get away from 6 stars unlocking an achievement (you might want to bring a car!)
a turismo (ferrari) dealer can be found at the intersection of Pyrite st and Bismark ave, east of middle park, on Algonquin island. it has like 8 ferraris but youll get a star when you steal one. who cares though! theyre ferraris
An nrg 900 (fast motorcycle) dealer can be found at the intersection of Lemhi St and Sacramento ave at the northern section of Alderney (west island). like the ferrari dealer, youll get a star but can lose it easily when you jack it
a skate park can be found on the west coast of Algonquin, directly west of middle park
IMO the funnest jump in the game is across a river. it is found on alderney directly east of Mahesh ave. its directly west of the skate park. mahesh ave is in an L shape. start on the western part of the east-west portion of the street (start at the corner). gun it to the jump and youll make it with a decent car
have fun