This is what I do: I close the zoo first -- guests are SOOOO annoying, the staff are bad enough. Then, I use a themed window fence according to the animal specie(s) in the exhibit. (unless the animal(s) can't use it)
Rainforest -- Bricks
Savannah, Scrub, Desert, Grassland, Wetland -- Wooden
Forest -- Concrete (there's nothing that seems to match)
Tundra, Alpine -- Tundra Themed
Then I put food, shelters and toys. I only put those that look natural, with few exceptions. Then I use the biome brush. I usually put a deep pool for animals that like swimming, and shallow ones if there's animals that like swimming and those that don't. If there's only those animals that don't like swimming, I just put water dishes and no pools. (Just because an animal can swim doesn't mean it likes it/often does it in real life. Lions for example I don't put pools). Then I add a few staff gates and add the staff. Then I move on to the next exhibit. Nothing fancy really.
That's how I build normal zoos, but sometimes I make certain "projects" like national parks, battlefields, obstacle courses, swimming pools and even live lizard hunting grounds.