Gulf Shores, AL
Good advice from drharris. Cosmo's, Tacky Jack's, Lulu's, Shrimp Basket...lots of good seafood. I'm not a fan of GS Steamer, but some people like it. In addition to the Canal Road location, Doc's has a place on Hwy 59 at Sawgrass Landing in Gulf Shores. Haven't been there, but the original is pretty good. For breakfast or lunch try San Roc Diner in the San Roc Cay shopping area.
I'm from the area, and for the best fried shrimp, it's definitely Doc's Seafood. Anyone who's a local knows this. It's off of Canal Road, and it gets packed (hole in the wall). I was down for Mardi Gras last weekend, and ate there twice. A really cool place (once again, only locals really know about it) is Pirate's Cove. Everyone pulls up by boat, it's a wooden beer joint that has an awesome atmosphere. It's almost impossible to find unless someone takes you there. Great place to drink, go barefoot and listen to guitar. Don't go there for food, they don't serve much other than chicken fingers and hamburgers. But it is truly an experience.
I'm originally from Gulf Shores, so I'll bite (no pun intended).
If you head up to the Mobile Bay area, there are a lot of good hole in the wall places, but I don't know which ones are still out there so I wouldn't want to get you lost. Just be on the lookout for vague signs like "shrimp" on the face of a gas station, something that looks like it was painted 50 years ago. That's usually a good place, but no guarantees. Probably safer to stay with known restaurants.
The best thing you can do is go into an actual seafood market (you should pass about 6-7 on your way into GS - look for the "we pack to travel" signs), and ask them where some good cooked seafood is. I personally recommend the Original Oyster House (http://www.theoysterhouse.com/). It's not a hole in the wall, but it's solidly good seafood of all types, never disappointing, and of course it's fresh.
You may also check out http://www.gulf-shores-alabama.net/gulf-shores-restaurant-reviews.html
Out of those, I recommend Cosmo's, Giggling Grouper, Tin Top, Shrimp Basket, The Undertow (great sandwiches), Lester's, Lulu's (Jummy Buffett Style), and Bahama Bob's.
Most of all, call the places before you go to find out if/when they have live music. There are a LOT of non-famous incredible musicians down there, you'll find a lot of bluegrass and country and southern rock. That way you get the full experience. :)
EDIT: I almost forgot two of my favorites. Gulf Shores Steamer (http://www.gulfshoressteamer.com/), try some of their Royal Reds. And, the Pink Pony Pub (http://www.pinkponypub.net/), good for atmosphere and good food too.
Overall, you really can't go wrong down there unless you visit a chain restaurant. Also, if you try to go with "fancy" food, I can guarantee you it won't be good. Stick with the basics. :)
A few summers ago we were in GS and I have to say that, without a doubt, the two best places in that area are Original Oyster House and Gulf Shores Steamers. Get a bucket of Royal Reds and it comes with a pitcher of beer. Great for two people. We loved it.
Also, if you go to Dauphin Island, look for a place called the Pelican Pub (It may have been wiped off the map though). We had amazing po' boys there.