I'm going to post mine, but definitely post yours.
1. Anything can happen. The PS3 went from horrible console to the best fun I've had all gen.
2. Don't wait too long to get a console. I waited till 09 to get a 360/PS3 (already had Wii). I was constantly playing a game of catch-up.
3. Any trailer that does not have uninterrupted gameplay footage is misleading.
4. Don't believe the hype. Zelda, GTA and Halo especially.
5. Don't focus so much on graphics. Gameplay and storytelling are more important because they age better.
6. With lots of review websites emerging over the past 7 years, GS's opinion isn't as important anymore.