Once your invitations have gone out and you begin receiving RSVPs, then comes the game of musical chairs while you configure a seating plan. You can go with round tables, rectangular tables, picnic tables, there are many options.
One thing you'll need to decide with your caterer is are you going to do a sit down dinner, buffet style, or hand passed food. This will help you determine whether you need to make an actual seating chart. If you are doing a seating chart, try to take into consideration who knows who and if there is any family drama to separate people.
If you're doing buffet style, you can do a seating chart or you can let everyone sit where they want. It totally depends on the atmosphere you're trying to have at your wedding. Seating chart says more formal while sit wherever says more relaxed. Take some time to discuss these with your fiancé and decide which options best suit you as a couple and your wedding.