From my experience:
1. Be ready for a variety of debate. You'll get a lot of traditional schools that don't really go to any national circuit tournaments and you'll get teams that are much more progressive. Similarly, there are a variety of judges, many are lay, while others are a similar quality to what you see at higher end tournaments.
2. Again, there's a lot of variety - you'll see teams that debate the way you are used to, and teams that are totally different.
3. Work harder, know your arguments better, try to utilize your resources to the fullest of their extent. Obviously, smaller schools will be at a disadvantage, but that doesn't mean you can't overcome it. Try to get really good at a certain type of argument (such as critical debate or T debate). This will help you become an expert, even without a coach to teach you everything you need to know.
4. Depends on the judge, I've seen some that would be down, but keep in mind that in many of your rounds you will need a good traditional strat.
5. Plan beforehand, determine what your strat is going to be and prep the hell out of it. Do lots of practice rounds/speeches. Don't underestimate the utility of lay debate - if you can make a lay judge think that you're a powerful speaker, you'll be able to win rounds even when the other team may be beating you argumentatively. Keep in mind that you only need 8/12 ballots to break - it's okay to split a few panels; don't sacrifice your ability to win one ballot by trying to get both (if you get two judges that are the polar opposites in terms of paradigms).
I'd say the biggest thing is to be able to adapt to your judge - don't try to get traditional judges to vote on progressive strats, and vice versa. The the thing that successful NSDA teams have in common is that they're very versatile.