Play your game. If it is a course you know well, don't change anything in how you approach each hole. Every player is going to choose to play a specific hole differently. You know your skills the best, what you're capable of doing, so don't try to do too much.
Talk to the TD about where he thinks you'll have the best time playing based on your average round score. Don't be surprised to shoot slightly worse than you normally do.
The major rules you need to follow are:
1) ALWAYS throw from your proper lie. You will need to have a supporting point (foot or knee) directly in line with your disc or mini. And you can not have your opposite foot or knee beyond the imaginary line extending across your lie.
2) When within 10 meters of the basket (about 10-13 paces depending upon your pace length) you will not be able to step past your line without demonstrating balance (having your body come to a complete stop) before advancing forward.
3) Common courtesy. Don't throw on groups in front of you, no excessive swearing, no cell phones, farthest away from the basket is the first to throw, etc ...
If I am playing with someone at their first event, I will almost always give them the benefit of the doubt. Before the round starts, I'll ask them what they do know. And if they happen to break any rules, I am going to mention it to them afterwards, as a "hey, this is what you just did, this is what you should do, no big deal" and give them two or three notices.
I've been given the same courtesy recently. A player in my group saw me unintentionally commit a foot fault on a long approach where I used a run-up. Without realizing it, I did it again a few holes later, and he made a comment about being more attentive to where I was placing my feet. Well within the rules, and we both handled it appropriately. Most of the time, rule violations are handled in a friendly manner like this.
Last thing, don't carry an excessive amount of discs or gear. Tourney rounds are long and tiring, and the last thing you need is extra weight on your back.