Tip 1: Arrive Early! If you don't have a table reservation, get there early!!!! I remember my first Oktoberfest when I had no idea how it worked and leisurely showed up at 3pm. Thankfully, we were a party of two so it was easy to cram into the outdoor tables. Keep your group to four people maximum in order to be able to get into the tents. Although the environment is a lot of fun all around, the best experiences take place inside a tent: sharing beers with perfect strangers, and singing songs in German you never knew existed.
Research your tents! The Oktoberfest website gives you a great guide of the tents and what they have to offer. Some of my favorite tents are the Wildstuben, Hacker, and Weinzelt. I love the rustic details and the traditional cuisine at Wildstuben. The Hacker is the traditional large tent that is perfect to stand up on the tables and party! The Wienzelt is a non-traditional tent as is serves wine. It has a great bar with lots of Sekt (German sparkling wine). I'm sad that one of my favorite tents, the Hippodrom will not be at the Wiesn this year but I am sure there is an equally fantastic tent to replace.