Sean,
29, young? Heck I started at 16 and am 29 right now. This is my 10th season working FB. So no, 29 is not to young. Actually, it is a pretty good time to get started.
As they said, contact a local school and see where they get their officials from. If they get them from an association, ask for the assigners name and phone number. If they hire them on their own, see if they would be willing to pass your name on to some that works for them. They probably won't give you individual names outside of an association, but who knows, maybe they will.
Start network now, this season isn't too soon. Find a local HS official and tag along to their game on Friday nights. Most crews will let you sit in on pregame, walk the field during the game, and ask questions if you have them. Remember, there aren't any bad questions. You might ask some foolish ones, but that's the best way to learn. Trust me, I've put my foot in my mouth a few times. Another thing in regards to asking questions/chatting with veteran officials, listen more than speak. You reduce your risk of coming off like a know-it-all that way.
Get registered with CA's high school league. Might be a little late for that but look into doing that next year. Think about purchasing the rule books. Since you will start off working underclass ball and the fact that California uses Federation rules, you can order this year's rule book at
www.nfhs.org if you like. Don't pay too much attention to NCAA or NFL rules right off the bat. They're different and you don't want to confuse yourself too much.
Last, (I could go on and on) read the boards here and elsewhere. You will learn a ton of stuff. There are some things you probably shouldn't learn, but you will learn more here than reading the book alone. Also, check my site. I've collected numerous files from officials all over the country, and world, with tons of great advice and insights.
Welcome to the group. There is nothing better than officiating. It is a great time, you'll never regret your decision.
Grant