If you need to get the attention of your server in a restaurant, try to make eye contact with them to get them to return to your table. If they are busy, and you’re unable to get eye contact, ask another server to tell them you would like to speak with them.
Never, under any circumstance, snap your fingers to get a server’s attention. You may have seen this work on the silver screen, but it will not get you favorable service in the real world.