If you have dietary restrictions (i.e., vegetarian, don't drink, etc.), just don't make a big deal out of it. Try to not bring direct attention to it - i.e., don't mention that you don't eat meat b/c it is cruel to animals or something if someone mentions that the steak is really good. If they order a bottle of wine, just take a glass and sip it w/o drinking. No one will notice if you don't finish it, but they will notice if you make a fuss about not wanting a glass of wine. You want to appear relaxed and comfortable, and not too picky.
Also, try to refrain from asking the waitress for her phone number while at dinner.