The Clove Hitch is a knot which is both fast and easy to tie and when done correctly, is very secure. The following video will demonstrate two methods of tying it.
If your rope is long enough and strong enough, it will support any weight including your own and still untie easily. You can practice this on the wooden arm of a chair or a handrail. The end should be long enough to go around the object about three times. If not drawn up tight, this knot is prone to slipping so throw a half-hitch on the standing part with the bitter end for safety.