I have some mates who can tie a "truckers hitch" - and this one seems to be by far the best i've seen. You can easily adjust the tension on it once the knot is in place - and any pulling force on either end only tightens the knot further. Only problem is I havnt been able to master tying it by myself yet - it is not the easiest knot to learn.
Actually, its called a sheet shank. Its a pretty handy knot. if you use a hard nylon style of rope, it can be a problem, but if you use an extra twist and loop on it, its fine. If you can't tighten a bowline, you just need practice. its a pretty easy knot to learn and takes no longer to tension than a sheet shank.
I personally like a little slack on the rope to let the aircraft wobble about and do its thing in medium winds. never hurts to throw a couple of chocks under the wheels either.