Unlimited Lasersight ammunition
Have the crossbow or revolver combined with the Laser-sight. Zoom in, hold L then press Start. While still holding L, select the pistols and press A. While still holding L, exit the pause screen. The sound of the pistols being drawn will be heard. Note: This can be repeated as needed.
Press L + R when Lara does not have any weapons in her hands to light a flare.
Turning on all the switches in the Star Room in the Lost Library:
First, start at the switch across from the reset pad. Face the reset pad and number each switch starting with the one you are at as "1" and then going left, 2, 3, 4, up to 7. Then, activate the switches in the following order: 1, 3, 2, 7, 5, 4, 6.
Save health packs
You can save health packs by going to a different level, then coming back for health because the levels are so numerous and close together.
Save explosive ammunition
Save explosive ammunition (grenade launcher, Cross Bolt, etc.) for tougher opponents when fighting the skeletons by using the shot gun against them. Get the skeleton between you and a ledge and blast it. The skeleton will fall off the ledge and cease the exist. Since shot gun ammo is more prevalent in the game than the explosive ammunition, this will allow you to save it times when there are no ledges to help.
Level 1 golden skulls
At the beginning, take a left up the small ledge.
In the room where you make your first jump, drop down into the water and go in the middle of the water.
In the room with the where you have to make two more jumps, fall down at the beginning. Run to the far end and turn to the right.
In the next room where you have to swim -- swim down to the bottom in the center of the room where the floor goes down slightly. Note: There is also a small and large medipack in a back room which is also under water.
In the area with the two boars, go around to the back and find the exit. Do not go in. Instead, turn right and go forward.
In the room where the skeleton has been impaled with the spikes, take a right when you enter.
In the crawl space, go to the left when you enter it.
When you get to the area just past the place where you have to "dive though the gap", go to the right and past the railing.
Note: When Lara gets all eight golden skulls she will chose a different, harder path when Von Croy asks her where she wants to go.