I have been making my own napkins for years; tried all sizes and fabrics. Now I routinely cut them at 18" square and I can get 4 out of a yard. Then I press 1/2" over around all four sides, then sit down at the machine and fold under that 1/2" to 1/4" and sew them down. As for fabric, I uses whatever feels good and is washable. I use mostly cotton and cotton blends. One of the things I did early on, was to go to a place like Home Goods, or Penny's or Macy's and take a look at their dinner napkins and see what you like. Then go home and make them the same way!