Good stuff from Treetramp and Oldtimer. Here's how I rig my adjustable lanyard. The hitch is a Knut but any closed hitch will do that works* (*test low first). The rope is 20 ft. of 11mm Blaze. The hitch is made with heat resistant 8mm prusik cord. The pulley allows you to take in slack one handed when you're tightening the lanyard. The hitch can be released safely with one hand to loosen the lanyard.
As mentioned beware of the biner or rope snap when you're pulling the end of the lanyard back though a crotch. The usual cause of getting whacked is the biner jams in the crotch, the climber pulls hard to dislodge, it comes straight at their face with a load of pain.
If there is a possibility that the biner will get hung up in the crotch it's very easy to slide the biner out of the termination knot, pull the knot apart and pull the bare rope end of the lanyard over the branch.It's very quick to re-attach the biner to the end of the lanyard after you take it off. If you have our friend Nick put a tight spliced eye on one end of your lanyard you can take the biner on and off even faster.
I attach my lanyard to the center delta as Treetramp advised. It is very uncomfortable to hang on the side D's. Side D lanyard attachment is typically used when a worker is standing on spikes and chunking down a tree.
More photos
-moss