A method that works well for me is to lay the hammock on the ground between two trees that are about 5-6 of my steps apart. If I have about 1 meter either side of the hammock to the tree, I wrap the webbing around the tree at just above head height (i'm 6"1) and tighten\adjust until the both hammock ends are level-ish and the bottom of the hammock is at butt-cheek height.
If the gap looks about 1.5 meters, I go as high as I can reach. If the gap is greater, I simply look for 2 new trees.
I'm lucky 'cause where I hike, there is rarely a shortage of good trees.