Welcome to the sport!! It will be a lot of fun. Snipe33 has some good suggestions. Also bring some small trade items (I keep several in my pack). I started off with the easy ones close to home because I am familiar with the area and it gave me a chance to get use to my gps unit.
First and foremost, be safe. With any sport, if you are not comfortable with it, DON'T DO IT. If it's too hard, then you lose interest. Get your family involved as well. My kids love to go out and look at the "treasure".
Have fun and be safe!!
DiverMan
Dive Down, Dive Deep