Extra Hunters
Beat an entire area in career mode then save and exit the game. Reload the game and start a new career to access the extra hunter. A hunter is unlocked for each area finished.
Get X Ray Scope
Get all tags in a level then play the area a second time using quick hunt mode. Press X while using the scope for X-ray vision.
Break the Law
If you ever shoot a non-game animal and don't want to get busted, just return to your Trophy Room to wipe the slate clean.
Easy Money
In career mode buy a tag for wolf in Alberta, or coyote in Texas. The tag will only cost $200, but if you kill all 4 of them with one shot you get $100 for a clean shot bonus. After you kill all 4 of your animals go back to the main menu and into location, go to the store and you'll have $200 more than you started with at the beginning of your last hunt.
Avoid Charging Animals
Getting into a vehicle will save you from suffering damage from a charging animal.