Check the weather report first. They're playing outside this year. Make sure to smuggle in a flask. You don't want to pay stadium prices for awful stadium beer.
Also, prepare for crushing disappointment whenever the Minnesota Vikings are involved. Trust me, I've been wasting every autumn for the last two decades on that pathetic excuse for a franchise.
Honestly, I'd look into a Wild game instead. They're less likely to suck and it's a LOT more fun. NFL football is awesome on TV because you can play video games or read a book or something during the down time and commercials, but it's not a great live experience unless you're drinking heavily. College football is good live, but the pro stuff is strictly a TV sport.
I'd warn about the crowd, as all us NFL fans are mouthbreathing scum, but I've seen how many people die in those soccer riots! We only get a stabbing or two per game, tops.