While it might not quite be on the same level as going on an African safari, a quick look around at some shots that people have taken at their local zoo is enough to reveal that a trip there can yield some awesome results.
1.) Get there early – Getting to the Zoo earlier than everyone else means that you get to take photos of the animals without anyone around to disturb you.
2.) Isolate the animals – Doing this allows you to get nice clear images with a single animal as the focal point.
3.) Group them up – Do the opposite of the above. Animals that tend to be social also tend to look better in group shots.
The longer you can spend watching and shooting each animal the better your chances of catching them in a wide variety of poses
A decent zoom lens or a telephoto can really be very useful
6.) Framing – Try and use the cage, a fence or a tree to frame the shot.
7.) Get friendly with the staff
clipped from: www.lightstalking.com