Delicas in herringbone stitch can be tricky: An easy way to keep thread tension.

I'm going to go right ahead and apologize for promising something I cannot post. I will be taking pictures soon of my fire polished/seed bead products, so those will be up later this week. (I need to start posting more)
So with that, let's turn to thread tension. I worship Nancy Cain's words mostly because she realizes the importance of thread tension and uses it to her complete advantage in all her pieces. Proper thread tension is always a complicated matter and almost an art to do it correctly. I know I'm redoing pieces I did years ago because I didn't keep proper thread tension and the piece didn't look as good as it should've.
With this piece, which needs a two tier tubular delica herringbone rope, I found the best method to maintain thread tension.

It might be a little difficult to see, but if you look carefully I'm holding the piece between my index and thumb, while my third finger is pulling on the thread and holding it against my second finger.

 Go through the herringbone as you would, holding that thread against your finger.

 Last step to arrive in the "up" position again (this is very important to keep the tension) pull the thread through the work until it's snug against your third finger. Pull your third finger away at the same time as you pull the thread.
This way, the work's flexibility is consistent and the beads are snug together, limiting the possibility that the piece wears down.
Another piece of advice with this piece, is to make weaver knots when adding new thread, instead of sewing in, knotting, and sewing in a new thread. The reason I had to redo this piece is because some of those junctions got a little loose and the beads were spacing apart. The structure as a whole is much more sturdy if you make it one whole thread.
If you don't know how to do a weaver's knot, here is a great website:  http://www.weaving.cc/leasesticks/knots2.html

Happy beading!