I've got some:
I'd not skip the keynote. ;-) And get there early. Ever since I scored a new mouse for showing up, I'm expecting some kind of keynote give away. Don't do that. It's perpetual disappointment.
I enjoy the Apple Design awards, but I'm less inclined toward the Stump the Expert session.
Take notes about the questions and answers, they are often the most interesting part of the presentations, but not included in the recordings online.
There is a WebObjects talk that is given by a guy (sorry, I don't know his name) but he always creates a song to explain what he's teaching at the end of his session. Sometimes two songs! They are just awesomely funny. I always try to make it to this session. And once again, it's not on the DVDs/online version you can view afterward.
The wireless network will be sketchy and most probably will not work during the keynote. Just know that in advance. Seems like it gets better as the week goes on.
Walk the floor both in the hallways and in the presentation rooms to scout out where the power outlets are. Often there are outlets in the floor, if you bring a small power-strip, you become fast friends will everyone around you.
Trying to schedule your sessions in advance is simply a lost cause. The keynote changes everything. You'll have lunch and time to think on the first day to plan the rest of the week. Don't be afraid to hop sessions, if one session is lame, jump to another one.
The feedback sessions are always fun, but by far the most vitriolic is the Aqua feedback session. I go just to enjoy the banter. :-)
Food goes fast. Get into the rhythm of when the food is set out and try to be there for the first drop. I almost always got the tail end of the Jamba Juices distribution which always meant, I got nothing.
Take some time to walk in the Labs and talk to the engineers. They are friendly and always have interesting things to say.
Oh, ya, there are lots of parties. Enjoy 'em.
The plug-fest is fun, just to see the new hardware devices people bring in to try out.
The Apple campus bash is fun, especially if you've never been there before. Unless you are on the first bus there, don't expect to get into the Apple Store on the Apple campus without a long wait in line.
What are your tips for attending WWDC?