Hey bud, dunno if this is too late or not but in regards to tourneys:
Obviously have fun, win or lose don't let it deter you from having a good time.
agree with trojan, the computer you can only do so much with (playing against another person will always throw in wrenches into your scheme while the computer will do some foolish things) however if you're stuck w/ the computer, play season mode and try going undefeated, the computer will progressively get harder and harder and it'll be more difficult moving the ball vs them (especially w/ the run).
At the tourney, personally i'd try and get as many pick up games as possible, before the tourney or even after (maybe even if there's a break). Any experience helps and you'll never know if you can pick up on something. Every tourney i've been to has been great, by that i mean the group of people have been nothing but nice and are willing to help out and explain to you why somethings are the way they are in the game. Very welcoming community.
If you're unsure of something, ask someone. There's usually no dumb questions. If there are i haven't heard it yet.
www.tecmogeek.com is another great site, it tells you the best players to use offensively/defensively for every team. Helps immensely w/ defense as to who to take and who to scheme against on offense.
As for team rankings, if you need help with that. Usually the tourney will provide a sheet for rankings, and if you call something that's really lopsided usually the other player will tell you so, if not, still not the end of the world. Learning experience/all for fun anyways. Plus if if makes you feel better i called zona/cincy vs mort in my first tourney, so there's that.
that's all i can think of for now. Best of luck in your tourney bud! Hope you have a great time.