It depends if you want to tailgate or not. Last year we showed up an hour or two before kickoff. If you plan on grilling food/drinking, or just wanna walk around and enjoy the atmosphere, try showing up around 1. Time flies quick out there. If you're really hardcore you can show up around 10 or 11, but you might be too hammered to walk to the stadium by kickoff.
Get there early and be prepared to boo loudly when they blow it. It's the only way to get McNair to make some changes.
I'm going tomorrow and planning to grab lunch at the nearby Pappasito's around noon, then head to the stadium immediately afterwards.
Then I would suggest getting there no later than 2. Parking takes a LONG time, plus it'll take you about 10-15 minutes to get into the stadium.
First experience = awesome. Had a friend drop us off at the gate around 1:30. Awesome atmosphere, took the lady around and got some nachos ftw. Great game!
Was a great crowd yesterday. I took my brother in law from Nebraska to his first NFL game and he had a blast as well.