I've made grids with overhead transparency materials and a laser printer. I lay out the designs with a CADD program (QCAD in linux and Visual CADD in XP), which allows lines of varying thickness and with patterns of dashes and dots. I use 6x7 and 6x9 rollfilm holders, and put these framelines on as well as a very light grid pattern. I don't like thick, obtrusive lines, so mine are mostly very thin and dotted lines that don't get in the way of the image.
Lee
P.S. I see Dave didn't mention it, but he has downloadable GG patterns in Adobe Acrobat format at his web site: Dead Link Removed