DIY ... HOW TOCut to Size: Measure your windows. My (two) windows are 6 feet wide and 8 feet high with a foot between the two (the ceiling is 9 feet high). So I made 4 panels (2 for each window). Each panel is 6 feet wide by 9 feet long (before hemming). I got this by cutting two 9x12 dropcloths in half. (They also come in 6x9 size, so you wouldn't have to cut them, if this is the size you need).
Square if up and hem: (optional) The ones I got weren't perfectly square or perfectly identical. The cloths ranged in length by 1 or 2 inches, so first I layed them out on the floor, picked the shortest one, and hemmed all of them to be that length. This was probably unnecessary since I let them "puddle" on the floor.
Decide on height & install curtain rod: B. installed one long curtain bar higher than the windows by 3 inches, but not all the way to the ceiling. (There is much discussion about how high to hang curtain bars these days ... somewhat higher than standard 7 feet is the current standard ... the height we chose seems about right to me, since my windows are already higher than std. 7 foot. And I didn't want the bar right AT the ceiling.)
Decide on how much puddling you want (if any). I read that in the old days of Victorian manor houses, the more puddling of expensive cloth, the more it indicated the wealth of the homeowner, as if to say "Look at the opulant waste of fabric puddled on the floor". So see my opulance!!! Drop cloth grandeur puddled elegantly on the floor. But how much? I read 3 inches is "plenty", 1 inch is "a little" (or some such guideline). Mine ended up being about 3 inches. You have to allow for this as you decide on how high to hang the rod and how long to hem the curtains.
Clip on the Clippies: I used black rings with clips (from JoAnn...half price on all curtain supplies), and clipped them on every 7 inches.
Hang them and (optionally) train them into pleats. In the top photo you can see how I pleated them, then tied the pleat with a ribbon and left them to be "trained" for a couple of days. It did help.
Open/Close them: Mine look nice and full when open. When I close them (which I rarely do... only the rare day when the sun is so bright on hot days, it heats up the room too much), but when closed, they don't look all that snazzy. Not much gathering left when closed ... but they're FUNCTIONAL, which was the point. And I keep them open 99% of the time.
The Color: Mine are an outmeal color, a pale grayish beige. A friend (hi, Diane!) says the ones she bought at Sherwin Williams are more brown, but this oatmeal color is good for my palette, muted, not too beigy.
So, my recommendation, if you're thinking of making them ... go for it. It's so easy. And to be sure the color is right, pick up a package at the hardware store and bring it home for a color test...