Tess is pleased as can be with the little green skirt we made and we hope to knock out a couple more yet.  Tutorial here.  Basically you cut three long rectangles.  Find the widest part of the hips/waist.  First tier is 1 and  1/2 times the waist.  Next is 1 and 1/2 times the first.  Third tier is 1 and 1/2 times the second.  The length of the rectangles is your total intended length, divided by three, plus an inch per tier for seams and 2 inches more for the top tier to make the foldover waist.   That was clear as mud wasn't it?   If you want to make one for yourself this tutorial has an automatic calculator to figure your measurements for you.