Ok, so this is my first topic on the site, so let me know if I messed anything up. These are just things that helped me make 5 star zoos in freeform mode, I'll add challenge and campain zoos after, since I don't play them as much.
Freeform Zoos:
step 1. I usually start with a large flat map, like the large city zoo. That way you have room to expand, and don't have to do a lot of work on the map.
step 2. Close your zoo.
step 3. Start with the paths, instead of trying to do the paths, exhibits, and guest items all at once. I always make a little area near the entrance to sit down, along with some flower beds and a few food carts.
step 4. Once you've finished the paths for the start of your zoo, move on to guest areas, such as bathrooms, food carts, gift shops, and anything else that will keep them entertained. I always make a little area near the entrance to sit down, along with some flower beds and a few food carts.
step 5. Once you've made the entrance to the zoo, figure out what animals you want. It's better to use animals with a lower star rating in the front of your zoo, and work your way up to 5 star animals. That way, guests will have to go all the way through your zoo to see popular animals. Some good animals to use in the front are koalas, fennic foxes, Thompson's gazelles, peafowls, and other non-endangered animals. In the back of your zoo add animals like lions, pandas, and dinosaurs (if you have EA).
step 6. You can build your exhibits now. Make sure they are big enough to include not only your starting animals, but any babies they might have. For some animals, such as elephants, you will have time to expand the exhibit, as they have a long gestation period, while others, such as koalas, breed very, very fast. Keep in mind that animals that do not use shelters will still need a place where guests cannot view them, so use trees, rocks, plants, hills and valleys to give them some privacy.
step 7. Place a zookeeper in every exhibit and assign them to that exhibit only. Add a lot of maintenance workers, a few educators (if you have podiums), and, if you have EA, entertainers.
step 8. Go through your zoo to make sure you have enough bathrooms, food carts, benches, donation boxes, and employees. Don't forget to add flowers and trees, fountains, and statues to make your zoo more beautiful.
step 9. Now you can open your zoo. I always set the price on low to begin with, but I don't know if it really makes a difference in the amount of guests you get. If people don't seem to like your zoo, read guest's thoughts, they can tell you what to do to make your zoo better.
Tips on Campain and challenge zoos are coming, I'll update this as soon as I can.