Nathan and I had a chance to join the festival in 2014. We went to see the parade on the opening day and followed the crowds toward the fairground. It was like Disneyland in Munich! The biggest fair I have ever been to. Most people dressed up in traditional German clothes and went to the huge beer tents. You had better get in there before noon; otherwise, you will never get a seat.
There was a traditional costume parade on the second day of the festival. We went to see it briefly before going to a party elsewhere. Overall, the festival can get crazy as lots of people get drunk and fight over nothing. Hotels can be booked up far in advance. Trains, trams and subways to the fairground are always very crowded and full of drunk people. However, it's fun and people can loosen up a bit. ;-)
For more information about Oktoberfest, check out its official website: http://www.oktoberfest.de/en/