Agility is sooooo much fun, and so positive, and should always be fun for both your dog and you! My favorite agility website is
www.cleanrun.com. You can find all kinds of information, schools, events to go watch, and websites with all kinds of stuff. There is even an agility magazine called Cleanrun. A newbie, or anyone actually, can learn a lot from an agility discussion list, and the cleanrun site lists many of them. There's even a Might-Mite list for small dog handlers (hmm, I may look into that one).
I'm doing agility now with my YT, a girl I got when she was nine months old. Not competing yet, but doing it over, I would definitely start her on a wobble board to get her use to movement under her feet. I will definitely do this for my next puppy. Lizzie is not keen on the teeter.
A good site for agility equipment is
www.affordableagility.com Both NADAC and USDAA don't allow a dog to compete until they are 18 months old. The reason is to make sure the growth plates in the legs are closed. AKC allows a dog to start competing at 12 months.
I've mostly done AKC agility, but with my IGs. Lizzie is the first Terrier I've ever had, and I think she will be a fast little dog in the 8 inch class. She's really fun to train.