Kikopup has a grand video on clicker training. Here is the url for her FaceBook page, sorry have to go out shortly, so cannot look for the vid. but it'll be there.
http://www.youtube.com/user/kikopup/videos
To start you need to 'load/charge' the clicker. Just get eye contact with your dog, doesn't have to be sitting or anything fancy, and click/treat for around 10 times, that charges/loads the clicker. It is VERY IMPORTANT to treat seconds after clicking, even if you click by accident still reward, as the dog needs to totally associate the clicker with a treat.
You can use food or if you dog isn't food motivated toys as a reward/treat, and also, have some high value treats too, for those harder tricks.