It's nice to stay so close.
The advice above is good. My main advice is get something to eat outside the tents before you go in. There are lots of food vendor choices, just make sure you eat something substantial - you don't want to drink on an empty stomach.
I like to hit the tents about 3 pm. By then the people who arrived first thing are completely drunk and being carted out by ambulances (you will witness this first hand and know I'm not joking). The other big group arrives about dark. If you beat them in, you should be able to get a seat without too much wait.
You have to be seated to order a beer. Stay in the first tent you sit down in or you will spend your entire evening in line. I think I've spent most nights in Augistiner or Lowenbrau - but my only souvenir was a t-shirt from the Hofbrauhaus tent.
Everything closes at 10:30 (I didn't know about the one late tent), by then you may have met some people who invite you to go to a club and party till dawn.