I'm brand spanking new to this game. I've slept under my new tarp exactly 2 times, last night and the night before.
I used 2 piece ridge line because my tarp came with some short(ish) sections of guyline. I larks head around the tree, go through the tie out point and then use what I think is a modified taughtline hitch. I saw it on one of Hennessy hammocks' videos and thought it was awesome. The not works a lot like a prussick. In my two nights, one with moderate wind, they haven't slid on me.
So, I use a two piece because that's what I had handy and, I'll admit it, I just plain enjoy tying the knot.