I'll start this off. I have one, 54" sq. (I'm 6'5" tall ) I started by laying it on a table (or floor if you find that easier), folded it in half on the diagonal to produce a triangle, then pleated it several times by folding each side in half again several times. Fastened with a large brooch to hold the shape. I use it for formal events only. I have seen others that were about 1 by 1 1/2 yards rectangle, but again usually pleated or gathered the same way.

As far as fastening it to a jacket w/o epaulets, a large nappy (diaper) safety pin on the under side should keep it in place, and do no damage to either plaid or jacket.

I'm sure you will get ideas from others.