I don't have a restaurant or work in one...other than to work with fine restaurants as a decorative(faux)finisher, stained concrete and venetian plaster artisan and yes we do some quirky site specific art...but I actually do work in restaurants and since i've been on twitter i've encouraged some of my clients to give it a go.
set up a twitter account and put the name on a blackboard, ask customers to follow.
1. tweet sport games that are on the everblasting flat screens.
2 have an american idol night tweet your favorites
3.specials kind of a no brainer. but it can increase traffic by listing local fresh ingrediants in a special salad, sandwich no no carb day...
4tweet changes in your restaurant or bar, remodel, new color,
5.tweetups. you can make your space available to alumni groups, after sports tweet ups, organized groups or misc groups, singles, and twitter about what you are doing.
If you have a dinner rush between 5-8..and quiet until when you close at 10 or 11 why not open up as a tweep up and use twitter to illuminate your big idea.
The photos taken at the top are from spitz. the traffic from an informal downtown la gathering was all social media.