Went every year (many times) from 2000-2003
As pointed out it's best to get there early so you can get a seat. You can't smoke inside the tents anymore so that is going to be a complete nightmare if any of you smoke as getting in and out of the tents is crazy.
I managed to break my leg one year, on a spinning disc which they did boxing on, and a couple of weeks later drank so much that my heart went into 'atrial fibrilation' and I had to have cardioversion.

But don't worry too much about that, I've since found out it would have happened at some point anyway as I have a minor heart condition.
My favourite tents are the Hacker-Pschorr one or the Schottenhammer ones for the most 'traditional' evenings. Most of the tourists go to the HofBrau tent, you're bound to see a few aussie ladies lifting their tops up there on the table, plus loads of drunken tourists.
After the fest is over maybe head over to Ostbahnhof to the party area there, there are loads of clubs/bars all in one area. If you're a bit older then go to Schwabing, take the U6 to either Gieselerstrasse or Muenchner Freiheit station and you'll see a nice road of bars and restaurants.