I use these tips in the following games.
For Scenarios:
-never use fences, use ditches
-if you don't like ditches, use cliffs surrounding 3/4 of the exhibit and put a fence around the front
-do not waste money on silly things, by the cheapest enrichment object, cheapest trees/plants/rocks
-focus on reaching your goal, if you ignore your goal you'll forget about it
For Challenges:
-use the tips from Scenarios section above
-try not to accept a difficult challenge unless you have the required items
For Freeform:
-dream, imagine, and believe
-there is nothing more fun than being able to do whatever you want in your zoo
I hope you enjoyed my tips. I use them and I have completed every scenario in the game. ;D