From the start, walk this route: right, left, left, right, right, right, left, left, left, left, right, right, left, left, right, right, left, second left, jump into the hole, walk through the hall, turn the switch and a door will open in Lara's house. You can get here flares as well.
Blow yourself up
Take 1 step to the left
Take 1 step to the right
Take 1 step to the left
Take 1 step forward
Take 1 step backwards
Turn 3 times
Jump with a somersault forward or backward.
Cool cheat
During the game, Step left, Step Right, Step left, Step Backward one space, Step Foward One space, Turn around 3 times (either way), Then do a Forward Jump Roll To skip a level, Do a Backward Jump Roll To get all weapons and health packs.
Level Skip
Using the R2 button: step left, step rught, step left, then use R1 to walk backward 1 step and forward one step, then turn completely around 3 times, jumpforward and press the roll button, Lara should freeze and sort of looked squashed, you will see the available cinematic for the end of the level. Warning do not try this on the last level, it won't work, and besides I'd rather look at Lara in a nighty than see the ending.
Find the gold dragon medalian in Venice
When you get the boat, drive it until you get to the water fall, in the sewer and drive off. Don't go into the tunnel, go strait about 1/2 the way to the end of that passage way. Dismount your boat and dive all the way down to the bottem and lite a flair. By now you should see the gold dragon medalian.
Open two doors on upper level of Lara's Home
Complete the Assualt Course in less then 50 seconds and the top two doors in Lara's Home will open. Inside one is Lara's Entertainment Room which contains the key to the Weapons Closet. In the other is the Butlers Quarters.