When tying flies, start with a short tag end so that you do not need to go back and trim the excess thread. This won’t save you a ton of time at first but think of all the flies you have tied in your life and the extra couple of seconds you have taken on each of those flies to trim the tag ends of your thread. Add up all those seconds and we are talking about some serious time. It is also just an annoying extra step that is unnecessary. Get in the habit of starting your thread and leaving just a small tag end that you can tie down as you go. You can thank me later 😉
Previous Tips:
I prefer a long tag end. I may be an old timer, but I use the tag end, held at about 30 degrees to the hook, to guide a base layer of touching wrap thread onto the hook shaft. Then I cut it off.