Here is what I want out of a restaurant:
Food preparation. Meats should be tender, not overcooked, unless you order them burnt. It is better to under-salt than to over-salt. Vegetables should not be overcooked to the point of mushiness. Sauces should be subtle and complex, with no one ingredient dominating their flavors. Except garlic and chiles, of course.
Service. You should get a menu within five minutes of arriving, parties should be served in the order that they arrive, and you shouldn't have to use a flare gun to get the server's attention. There are two parts to service: the servers and the kitchen. I am much more tolerant of slow kitchens (``good food takes time to prepare, please be patient,'' reads a sign in many better-class establishments) than I am of inattentive servers.
Talk back!When you are not happy with your food or service, please don't just sit there and fume. Tell your server you're not happy and don't be shy about sending imperfect food back, if you have the time. All the restaurateurs I've talked to on this subject say the same thing. They want to know when you're unhappy, and they hate it when people stomp out without a word and then start a whispering campaign against the place. Finding, hiring and keeping decent cooks and servers is an ongoing battle for any restaurant, and customer feedback is the first line of defense against inept employees. You are paying them to feed you decently, and you have a right to tell them if they don't.