I also have a rubber lens hood that can be shaped to help block the glare and fit snugly against the glass of an enclosure, thus helping to block the ambient light.

  You can also make your own, all you need is a paper template and a black piece of thin foam or cardboard.

   A little more advice on glare, when you go out where you know there will be glass enclosures, be sure to wear dark clothing, as it can aid you in your battle against glare. Sometimes you can use your own body to block the glare on the glass from other zoo patrons. You can also take a small black umbrella with you to block out the bright colors of the crowd behind you. Just be aware you may attract some unwanted glares from fellow zoo goers, if your umbrella is to large. So the  smaller the better when it comes to umbrellas.

  Fencing can also pose a problem, the key here is to keep your aperture high and get as close to the fence as possible, sometimes doing this you don't even notice there is a fence in the finished shot.

Anyone can take a picture of an animal in an enclosure, but what you want to do is take the picture that highlights their beauty. The key here is patience.

  So, you found the perfect place, now you need to wait. Yeah, you heard me, you have to take your time (one thing my daughter will not allow me to have when she accompanies me to the zoo). Just so you know it is probably best to take these trips without the distraction of family or little ones. 

  You will most likely need to use a tripod so that your photo is not blurred due to shaky hands. So make sure where ever you choose to shoot from has enough room for your set up, without getting in the way of other onlookers. You may also want to go to the zoo on a weekday in the off season (i.e. not summer) so there are less people, but more importantly less children.

  You will also most likely have to use a distance lens, as it is not often that an animal will approach the glass for a photo shoot. (Thus, another reason that a tripod is necessary.) When dealing with a telephoto lens we all get started with the same one: the basic 70-300mm f/4-5.6. This is not a bad lens and is great if you don't have a lot of money to spend. Here is an article that goes over many of the telephoto lenses offered by Nikon and the differences between them. Just be sure to note the prices can get away from you, to well over $10,000.00.

What is a monopod?

   Everywhere in this article where I wrote Tripod you can substitute the word Monopod. A monopod is basically an expandable stick that helps you balance your camera and avoid the shaky hand, blurry shots. I actually just saw my first one in a store about a week ago... and I WANT IT! Now we will go over a few pros and cons of Tripod vs Monopod!

  Tripods are sturdy, and capable of holding your camera without your assistance which makes for beautiful shots with long exposure photography. They also help you keep your camera focused on a central subject without much effort, for the days that the animals are being boring, then suddenly leap into action. However, they are bulky, and get in the way in a crowded environment like a zoo. They are also great for studio shots, macro photography, and a must in time-lapse photography.

   Monopods help when you don't want your shaky hands to blur a shot. They have a quick setup and are much less bulky when carried. When in a crowd they are ideal due to the much smaller foot print. They are also better if you come upon a habitat where the animals are being quite active, as you can easily follow them while having the support you need to hold the weight of your camera. I know a lot of times when using my tripod, I never extend the legs out and use it as a prop on a fence or other solid object to get a quick shot of a moving target, a monopod would make this practice much easier.  However, a monopod will never be able to replace a tripod, even if they have the tiny "tripod" like adaptor for the base of them. They lack the ability to hold your camera in one position for those long exposure shots.

Try to find a way to stand out from the sea of cameras and grab an animals attention!

  I have heard some suggest that you should take a toy that makes noises to grab the attention of an animal, but in my opinion this should never be done, as the toy could fall into an enclosure and become a choking hazard to the animal. 

  I have found an alternative. They sell "Shutter Huggers" which are basically a stuffed animal you attach to your lens with elastic, like a hair scrunchy.  These are a trademarked item and well I think that you could try and make one yourself for cheaper.

There are Crochet Lens Buddy Patterns out there, or you can just glue one together using felt and a hair scrunchy.  Just be sure when you are making them to make them colorful and interesting, they don't even have to be animals, they can be flowers, or anything you can think of. (Note: These are marketed for taking photos of children but animals will usually be attracted to them as well.)