If a seafood restaurant smells too much like fish, leave immediately.
If the restaurant menus are not clean, chances are that most things won't be.
Pick places with a short menu. They are more likely to have skilled chefs.
If a raw item is claimed to be fresh and it not found anywhere near your area then chances are, it is not fresh.
Other than the menu, see reviews on staff and if they are courteous otherwise it can ruin your experience.
The buffet system is hard to keep sanitary so pick only the top rated restaurants in terms of hygiene.
If you smell grease in a restaurant, chances are their kitchen exhausts are not cleaned.
If you order a big dish and it takes less time, it is likely to be pre-cooked.