-Bring your drinking face.
-Grab yourself some Canadian beer.
-Wander around with your friend and just take in the scenery, there's usually crazy games, stunts, etc. going on in many of the tailgating lots.
-I wouldn't worry too much about having a Texans jersey on. You'll get the occasional yelling and shouting and booing but just act friendly and happy and no one will care.
-Pound those last few beers on the way to the gate, seeing as beer prices inside are ridiculous.
-Hit up Duff's after the game if possible...you won't regret it.
-Definitely be prepared for the weather, it will probably be very cold.
-Get to the tailgating lot early and start drinking, start the day out the right way.
-Enjoy yourself, it will be a fun experience.