Have a look at Knotting Matters Issue 6 - Winter 1984 - page 2. There is an article by John Constable on this very subject, covering both four and eight strand square sinnets. I confess I found it difficult to follow although it seems absolutely perfect. There are also some clues in Ashley No. 3001.
I use a quick and dirty method which passes all but the most picky inspection. Descriptions without pictures are difficult but I'll try. As I tie it, I say to myself "left, right, left, right".
Divide the 8 cords into 2 sections, left and right. Let them find their own positions. Look at the right hand set of 4. Pick the one that appears to be most on top and most near the center.
This selection method; "most on top, most near the centre" is used for subsequent selections. Note that once a cord has been moved, it is not moved again though.
Pass this cord to become part of the left hand set and say "Left". The cord will now be on the left hand side, closest to the centre and will not be moved again.
Pick the prominent cord from the left hand set and cross it over the first one moved to become part of the right hand set. Say "right".
Now pick the prominent cord from the right hand set and pass it over to the left hand side, passing over anything previously moved. Say "left".
No prizes for guessing the last move. The prominent cord from the left goes over to the right hand side, passing over the previously moved cords. Say "right".
Imagine you have been working on an eight strand square sennit and stopped to answer the door. You pick it up, inspect the structure and say "Aha", the next pass is this one here and it goes round the back and up through the middle of the bunch and so on. This is well illustrated in Ashley No. 3001.
Good luck.
