Each tent has areas where there are tables that don't have reservations. Good advice below that a friend of mine wrote up:
Arrive early!The tents open at 10AM weekdays and 9AM weekends and holidays. On weekends, I recommend you get there no more than an hour or so after opening if you have no reservations. On opening Saturday, I recommend you get there BEFORE the tent opens! Weekdays are not nearly as crowded but I would still try and arrive in a tent between noon and 2pm. Most all the tents have a "no reservation" area. Look for 'keine Reservierung" signs or ask a server. Tables being held will have a sticker that says "Reserviert."
- NOTE: Monday-Friday, tents must leave 1/3rd of the central floor areas "open" and w/o reservations. Saturday, Sunday and Holidays (Oct 3rd), the tents are prohibited from having reservations on the central floor at all. Only the Wine tent and Kfer's Wiesn Schnke are exempt from this rule. For the record, the central floor or 'Ship' as it is sometimes called, does not include the perimeter seating or any balcony areas.
- OK, you arrived late and the tent is packed... No worries. Provided there are no more than two or three of you, walk up and down the aisles and politely inquire to any patrons you see,"Ist der Platz noch frei??" or "Is this place still free?" in English. You will mostly get "nein" or "no" but don't be discouraged, keep trying. Another popular method is to stand at the side of the tent and look for people who are leaving. Be prepared to rush the table and stake your claim! These methods usually produce a seat within 10-15 minutes.
- "The tent doors are closed! What do we do?" If the tent doors are closed, you can be sure it is most likely a Friday or Saturday night and the tent is packed to overflowing. You have some options... Wander around to the side or back of the tent. Many times there will be a lot less people waiting or a wide open door you can enter. If you are in a group of people waiting there, don't let people elbow their way in front of you! It's every man or woman for themselves at these doors. Nice weather? Sit outside for a pleasant change to the crowded interior of many tents. The service is better and you can hear your tablemate when they speak! The best option: Go to another tent. Some tents are more popular but I can assure you, you will have a good time in all of them.