Hooray for the zoo! (I work there, so I'm a bit biased lol).
I usually recommend that you start your day off with the bus-tour (included with most tickets), which is a 40 minute tour that shows you most of the zoo. Then, you can go back and see the specific exhibits that excite you. The zoo is huge, so this is a good way to get a general idea and cover a lot of ground without walking too much in the beginning.
An absolute must-see is the pandas. Only 4 zoos in the country have pandas, so be sure to see them. Now that summer is over, the line is not nearly as long (could be more than an hour in the summer!), but still hit them earlier in your day (pre-lunch) to maximize your time. They do also offer "Inside Look" tours that cost a bit more, but get you on a small 10-person golf cart, so it's more personalized. You also get to stop and feed animals (which ones will vary), so it's a nice way to ensure a more memorable trip, but certainly don't feel it's necessary - just something to look into on the website if you're interested.
We also have LOTS of babies around the zoo! We had two baby giraffes born this year, so check them out in Urban Jungle across from the rhinos. We also have two baby twin tigers. Right now, they are only on exhibit in the morning (go in around lunchtime) so be sure to ask when you arrive about their schedule. We also have a baby hippo that is on exhibit half of the time, so hopefully you luck out and come on a day that he's out with mom.
Elephant Odyssey is one of the newest areas in the zoo (opened May 2009) so spend some time there as well. Polar Bear Plunge is a newly redesigned exhibit that opened last year with lots of interactive parts for kids, so check that out as well - very cute.
I actually like the food in the zoo a lot, but you are always allowed to leave and come back later in the day if you wanted to eat somewhere else.
Let me know if you have any more questions!