Oktoberfest

I went to Oktoberfest in 2015 with my sister in law. I tried finding us a reserved table, but each tent that I emailed wrote back and said that I. Could only make a reservation for a large group.
We went to the festivities on two different days. Didn't have any problems get a table. Others would join our table or we'd join theirs.
The worst part I found was the very crowded subway stations and trains to get to the fairground area. Once out of the station the crowded seemed to disburse. Leaving the fairgrounds wasn't an issue.
Walk around and check out the different tents, really cool.
Enjoy !

As the previous poster mentioned, reservations are only available for full tables of 10 with a mandatory purchase of a drink and a meal totaling ~200 euro. You can also find tour companies that offer a quick tour and wind up in a tent at a table, but the cost is usually 50-100 euro p/p.

However, I have been twice with no reservations. Entry to the grounds and the tents is free, however you need to be seated at a table to get a beer. Rules for the tables are if one is open, you are free to sit. Each table has a reservation card showing the times that the table is reserved, many are only reserved from 5:00 PM til close for example, so you can sit there until 5:00.

Weekends are busiest, so chances of getting a table are reduced, I typically target a weekday afternoon, this last year our group of 4 was able to sit in any tent we chose, we did sit in 3 or 4 for a beer.

No. We've been in mid afternoon and had no problem at all getting into any of the tents. Early to mid afternoon is simply our preference since is does get very crowded at night.

If you are on a weekday you shouldn't have any issue getting into a tent. If you are there on a weekend they could fill up and close the doors. The earlier you get there better. You'll have no problems meeting people and making friends at any table with an opening.

I think people are underselling the crowds at Oktoberfest a little bit. I went on a weekday early afternoon and the lines for the tents were massive. We only got in because we befriended a worker on his break who snuck us into the Hacker-Pschorr (can't spell that damn beer's name) tent and then we were on our own for finding a table. We finally found one but we had to buy a guy a mass of beer and we were only able to stay for an hour before the evening reservation kicked in.

I will admit bias for the city in which I live but Stuttgart's Volksfest is nearly identical to Oktoberfest except it's managable. You'll still struggle to get into a beer tent on a weekend evening but weekend afternoons and weekday evenings you're fine, plenty of unreserved tables (no need to buy a beer for a stranger) plus nice outdoor areas at the Almhuttendorf for enjoying fest music outside of a tent (nice when it's hot because those tents really heat up!)

The crowd is more local, with some tourists from other parts of Germany, Austria, Switzerland, and Italy, but unlike Oktoberfest you're not likely to see drunken tourists puking all over themselves. There is of course an American contingent but they're mostly military folks who live here. Even though it's not in Bavaria everyone adopts the Bavarian songs, dress, etc for the fest. It's truly underrated as an alternative to Oktoberfest and it's only 2 1/2 hours away by train from Munich.

The reservation system is still the same. However if you find the "Stuttgart expat" group on Facebook you may be able to get in on their massive reservation (200+ people) and find yourselves with groups of friendly English-speakers for an evening weekend reservation. Just be aware that the organizer can be a little prickly about ticket distribution so be sure and tell him you're traveling from abroad and ask how ticket collection would work. He does do a bit of a surcharge but it's less than 5 euro per ticket so it's not too upsetting. Tickets are good for 3 liters of beer and a meal and cost around 40 euro.