I agree w/ previous poster--Hunan Lu is the place to be for great food at Nanjing's best restaurants. I don't remember the name but there's an excellent Thai restaurant there that all the locals rave about. Also, this is super vague, but maybe a local will know the exact name, there's an amazing restaurant on Hunan Rd that is known for their clay pot chicken. I don't remember much about it but I do remember that it's decorated like an old fashion chinese courtyard w/ windows for food on the side. There's a double bridge that you cross when you walk in the front door, a very large artificial tree in the middle of the "courtyard".
If you're interested in western-style food:
The Swede and Kraut is good--right off of Shanghai Lu near Nanjing University.
For good hearty breads and great desserts try the Skyways Bakery which is also near Nanjing U. There's also a great potsticker restaurant near Skyways. My directions will probably be worthless to you but---if you can find Skyways (which all the expats frequent so actual address shouldn't be that hard to come by). Starting at Skyways, you want to cross the street toward the supermarket and turn left (toward Nanjing Normal University, away from Nanjing University), the first street you come to, don't cross, but turn right. To your left will be a number of potsticker restaurants. If you arrive around dinner time, you'll notice that only one of them has a line of people waiting. Go to that one. The order process is to go inside the restaurant--tell the cashier you the # orders of orders you want (1 order=8 potstickers), pay, she'll give you a little tag and with your tag, go wait in line.
Also, don't miss the great foodstands that come out at night all over the city and some great breakfast foodcarts too. It's probably better to partake in them during cooler months for food safety reasons, but the food is amazing--wonton soup, stinky tofu (at Fuzimiao/Confucious Temple), squid on a stick, dumplings.
I lived in Nanjing for a year and managed to eat very well. Unfortunately, my memory is failing me on locations and I never knew restaurant names to begin w/ :). Anyway, hope you have a great time in China!!
1. FuZiMiao WanQingLou's snack series
2. Enjoy a pot of tea on the top of JiMing Temple. Or a bowl of noodles. Best View. Not sure if you can walk directly to the inner city wall though.
3. Go to Hunan RD and try the Lion's Court's DaPaiDang. You could also get the famous Nanjing Duck for take out on HanFuxin Duck house 2 blocks away. This is the bookstore/university district too. :)