Regarding long tree straps I do the following using 1" straps:
Tree end - tie a permanent loop using a "bowline knot". Pass the free end around the tree and thru the loop, cinch up tight around the tree. The knot reduces the strength of the strap, but the stuff I use is plenty strong to begin with.
Hammock end - attach a carabiner at any point along the free end using a forged climbing ring, carabiner, and a "line locker", see video below. I stole this idea from Slacklining.