I have the gear and now the toys; but lack for knot knowledge, like many noobs. But, it shouldn't be necessary to acquire any of them before dialing in a hang to as much fit and satisfaction and better methods will later offer.
Simplest way to adjust hammock hang, assuming a pair of not-too large trees AND straps -- straps are essential. With none of the gear, toys, or knowledge?
Adjust the wrap.
Wrap the trees with straps / huggers (and line, if strap is short), cinch, and run the strap and rope BACK around the tree, as though to strangle the tree. The length adjustment after the first try is now just done by loosening the wrap a little and turning the bundle to take up line or release some line. Be sure any line rests against and places the strap between the line and the trees. Tug sharply on the line to re-tighten the wrap on the tree.
Sure, this is obvious, but not if, following must illustrations, noobs like me assume the hammock suspension lines must come out at a right angle from the tree.
And it won't work with greasy straps, teflon-barked trees, etc
All the real marlinspike seamanship techniques are worthy. But the new owner / buyer ought to be able tweak, adjust, and find happiness with nothing more than straps (and friction.)
If this isn't to be trusted for an all-night hang, it is certainly an easy way to experiment and discover the length of a desired ridge-line.