Arrive with lots of extra time, print extra copies of boarding passes, and keep your passport in a pouch around your neck, UNDER your shirt.

Ask questions of airline staff and crew at any point. They are there to help!

Don't be intimidated by the big crowds at large airports. Just focus on getting to your next gate. Always find your next gate BEFORE you look around for food, sourveniers, etc.

And finally, I agree about avoiding alcohol. Also steer clear of the Ambien and other stuff like that. Make sure your mind is clear throughout the trip.

I flew alone starting when I was around 15 and it was no big deal. In fact, it was so much fun that I never gave it up!