Good link provided by Liz

that's how I got started too. Once you've got the dog understanding that click means reward (which Chloe seemed to get quite quickly) it's brilliant. I didn't do a lot until I went down to see Mark, but I have the clicker (and treat bag) at hand all the time now. I click any behaviour that I like and want to reinforce. At the mo, we're trying to use the clicker and a target to get Chloe to sit on a spot when she gets out the van. A work in progress

Important to remember that you don't HAVE to use treats, Chloe isn't very food oriented, so a play with squeaky ball, or lots of praise and fuss works for her as a reward too.