After I finished threading I put the back beam up and tie on to the apron in one inch sections. I push the beater back to the breast beam - then if I have any tangles the beater will come up to the castle. That's my signal to stop and untangle. I make one full rotation and then go to the front and give a tug. If the warp's not too wide I can fit half in each hand and tug. Some people go as far as putting the foot on the breast beam and really pulling, but I've found that the key is even tension, not heavy tension. This is where Cay Garrett's tensioning system can be used. You can also use lease sticks. Step on the tabby treadles and insert them in opposite sheds between the heddles and the back beam.
I usually put a piece of screen door molding (.75" x .5") next to the knots and start the paper there. The molding keeps the knots from popping through. If you have a very long warp you can also insert warp sticks every couple of yards.