In reply to Andy S: lots of tutorials on the trucker's hitch. I've been using this knot for years for all sorts of things - everyone should know it!
I recommend using a 'slipknot' instead of an overhand on the bight or figure-eight on the bight. Also, finish of how you would tie-off a belay plate - this is much easier to tie and much easier to undo.
The trucker's hitch creates mechanical advantage, like fancier setups do. If you use a krab it works even better. If you really want to go to town you could buy a little pulley which mean you could get uber-tension, but I've seen plenty of excellent results using a plain old trucker's with a krab.
Impossible to explain in text, good luck in finding a good tutorial!