Main lines of the tarp? Some people use prusiks, dutchware (this is my favorite) or multiple knots. I'm a fan of the Continuous Ridge Line and went ahead and bought a Single Line Tarp Ridgeline with Dutchware from whoopieslings.com
. They also have several other options, and can at least give you a few ideas of what people use.
They also have a guide which may give you a few ideas. And there are a ton of posts in this section of the forum about the same thing.