I guess this isn't really a climbing technique, but it's what you have to do first so....
This is by no means original by me, but I use this method A LOT - almost everytime I set a throwline unless the setting is trivial.
Many will already be aware of the method; it's pretty simple once you understand how to do it and it's advantages, which, BTW, are numerous:
1- it almost guarantees you won't get your throwbag hung
2- it assists in manipulating the throwbag in the tree
3- you can pull it down and start over, say to add an additional throwbag for more pull-down weight, without losing your current setting and progress
4- you can repeat it several times to clear difficult areas in the tree - I've done it as much as four times on one setting just being careful not to get a throwbag stuck
Due to 'technical' issues, the video is not quite as clear (i.e. how to do it and why) as I had intended, but here it is - there is additional 'verbage info' in the description on YouTube: