Level 1: Crabs
Look at every cave because crabs pop out of each of them.
Level 2: Crabs
Always look around you at the second cave and the rest of the level. Crabs will appear from everywhere.
Level 2: Conserving ammunition
Do not use all your shotgun shells on the huge beetles. Instead, shoot one shell at each bug that gets very close. You will have to fight a dinosaur after you open the gate.
Escape Velociraptor Easily
In the game, on the levels where you confront a Velociraptor, there is a glitch in the game. To take of advantage of it, all you have to do is simply break eye contact for a few seconds and it will go away. You could be standing right next to it and if it doesn't see you it won't eat you. This is very helpful if you run out of ammo, or if you want to use hit and run tactics with spears to save ammo.