I’m a big fan of arriving at the zoo early, before the crowds. The light is lower in the sky; the animals are waking up and usually active. There are fewer people around so you can relax, take your time and get the great shot of the day.
While a visit to the zoo is good anytime, I like going early. Check with your zoo’s website to determine when they open. Many zoos extend their hours in the summer so make sure you get the most up-to-date information.
While normal hours are great, we can also look for special hours. I know some zoos allow members special hours. Here in Denver, members can enter the zoo 30 minutes before the normal zoo hours during the summer. Those 30 minutes are golden. The zoo is practically empty and the animals are relaxed and natural.
Also, watch for local camera stores special classes. In many places, the local camera store will offer classes on photography at the zoo. These classes are a separate fee, but they get special access before the zoo opens. Also, the instructors are a wealth of photography information and provide wonderful Zoo Photo Tips.