Admission prices fall into five categories: Free ($0.00), Cheap ($0.25-$19.00), Normal ($19.25-$29.00), Expensive ($29.25-$49.00) and Very Expensive ($49.25-$100.00). Guests can only distinguish between categories, not incremental values within those categories. Whatever category you choose, set your admission price to the highest value or you're just leaving money on the table.
Guests don't distinguish between Free and Cheap admission, so make your lowest price $19.00.
Go with Normal ($29.00) to maximize attendance without sacrificing profitability. Restaurants make more money than food stands. They also cut down on trashcans and standalone restrooms. Focus on full service wherever possible.
Given a large enough exhibit, lions, tigers, flamingos, wildebeests and ostriches procreate with a vengeance. Happy hyenas and warthogs can also be prolific. Establish these exhibits early and sell animals to maximize cash flow. Particularly fertile aquatic breeders are tuna and Moray eels. Let poo earn you cash! The Compost Facility earns $50 for every pile of poo zookeepers rake. Purchase a Compost Facility early on, and place it in a back corner of your zoo away from guests and centers of activity. Adding additional facilities won't increase profitability, though, so don't waste time, resources or guest happiness adding more facilities. Gift shops positioned near the front entrance are generally more profitable than those placed elsewhere in the zoo.
Don't forget attractions: theatres and carousels can generate significant revenue. The ring toss can be profitable, but doesn't add to guest happiness or make very much, so skip this until you're very comfortable with funding.
"Recycle" (sell off) some of the trees and rocks that come with pre-designed scenarios and freeform formats.
Wait until the second month of your game to hire maintenance workers. Your fences will all be new, and you shouldn't have enough visitors to support the expense until at least the second month. If you load up on restaurants and keep trash-producing facilities to a minimum, you can even skip hiring maintenance workers until fences begin to deteriorate - 12 months or more into the game.
Don't over-fence. Some animals do just fine with low fencing, so save money here and use the less expensive short fence for their exhibits.
If you're restricting your zoo to only one pack (Zoo Tycoon, Marine Mania or Dinosaur Digs), click on Research and Conservation to deactivate any items you don't need.
Don't forget to periodically check your zoo financials. Look for buildings / attractions that consistently lose money and sell them.
One user creation that does more for zoo profitability than almost anything else is the Animal Adoption Center available through Zoo Admin. If you want a little help bringing in money, and aren't averse to user creations, head on over there and download it. One caveat, though: it seems to take the place of gift shops, so don't try to put a gift shop in a zoo with the Adoption Center; the gift shop will only lose money and eat into your overall profits.
Donations
Exhibit Donations: Happy guests pleased by an exhibit may leave a few dollars in the donation box. You can view contributions for each exhibit by selecting the "donations" icon on the Exhibit Information Panel.
Benefactors: Zoo members, Subscribers. Whatever you call them, these are the people zoos look to for reliable monthly income. Benefactors are pleased guests who will make a $100-$300 monthly donation to your zoo. You can only obtain benefactors as they leave the zoo; current guests don't sign up.
Emergency Donation: If your Available Cash falls below $1,000, you might be rescued with an emergency $10,000 donation. This only occurs once per scenario or freeform game, so don't look for another emergency bail out if you run short of funds again.
Endangered Species Donations: The first birth, and only the first birth, of each new Endangered Species will net a $10,000 grant. Make sure endangered animal exhibits are as close to 100 suitability as possible to increase chances of reproduction.
Panda Donation: You will receive a $50,000 donation for the first birth of a panda in your zoo.
Great White Shark Donation: You will receive a $25,000 donation for the first birth of a Great White shark in your zoo.
