The first thing I decide on when creating a composition for a photo is the background. Typically shooting these tree jobs, the background is the sky and there aren't many other options since the subject is high in a tree and I'm (typically) on the ground (sometimes standing on a truck or other higher perspective).
Busy foregrounds are typical when shooting from the ground looking up into the trees trying to find the climber. In order to minimize the limbs in front of our subject (the climber), I used the tree, crane, and branch he is standing on as leading lines to move your eyes over the fray of smaller branches with ease.
Looking at the image as lines, the biggest, thickest, boldest lines surround the subject. Framing it in the center of the leading lines ensures you take notice of it no matter where your eyes journey in the photo.