You can leave a soup spoon in a soup plate. Any unused silverware is simply left on the table. It is inappropriate to ask for a doggy bag when you are a guest. Save the doggy bag for informal dining situations. It is best to order foods that can be eaten with a knife and fork.
Finger foods can be messy and are best left for informal dining.
Do not order alcoholic beverages. Drinking too much when dining out is one of the most disliked behaviors. Do not smoke while dining out. Sit up straight at the table. It makes a good impression.