The Larks Head knot is the single most useful knot in kiting. You will use this knot to attach your flying line to your kites tow points (akaPig tails). The Larks Head is a slip knot, therefore the more you pull the tighter it becomes, so there is no chance of it coming loose in while the kite is in the air. As soon as the tension is released (after landing the kite) the knot is easy to pull loose and undo.
Check out this great video by Kitelife.com: