I leave figure 9 rope tensioners permanently attached to my MSR groundhog stakes. That way, I never lose them, and they are easy to adjust. The guylines are left attached to the tarp, with a girth hitch on a loop, so they are easy to remove and move around if I want to.
I can tie knots, and have used many of the methods mentioned here, but I keep going back to the figure 9's as they are really fast and easy to tension, and I don't mind the slight weight penalty.
+1 on the nines. I have tried other methods, and I keep coming back.
“Things are as they are. Looking out into the universe at night, we make no comparisons between right and wrong stars, nor between well and badly arranged constellations.”
― Alan W. Watts