The best site for purchasing clicker training books specifically, and agility training books in particular is Clean Run . I start by using a touch stick, or a target stick. These can be bought from the site referenced above, or you can use a dowel rod, or a retractable pointer, or a retractable radio antenna. You must also have a clicker, which can be bought from the site above, or from most vendors at dog shows. I prefer the clickers attached to a wrist coil, so that it's always available.
Timing is critical when using a clicker.
You must click the instant the dog offers the behavior you want, followed immediately by a treat. If you miss the timing, you might as well not click. I use String Cheese, because it's low-fat, inexpensive, and sticks easily to the stick. You could also use Bil-Jac, or peanut butter. It's important to use something that will adhere to the touch stick when it moves.