soooo, i've seen some posts with questions about pencil skirts, and it so happens i just made one!
i wanted something sort of like this:
http://www.chinatowner.com/storefront/viewDetailProduct.aspx?flagSide=0&sku=33484&color=Redi don't have a before photo, but basically i had long stretchy red pants with a tie-waist, and the crotch kept ripping, so i decided to make them into something without a crotch. i just took apart the seams, cut the panels to the length i wanted, and sewed down the sides in the shape i wanted- so there are 4 seams to give it shape, plus the stretchiness makes it fit well. the top-waist part i did separately, then lined the seams up and attached it, added some darts and a zipper. and big plastic buttons, of course.
here it is:


and the back:
not quite a smooth seam, as you can see. i'll have to iron it and re-sew.
alright, i've never made a tutorial before, so bear with me. here's how it goes:
turn yr pants inside out, and they're probly made of 4 pieces like this:

with a seam-ripper, rip apart the inside seam (the one with the check) but not the outside seam (the one with the X). Now you have two pieces. Fold each piece in half along the seam and cut on the red line (adjust the length according to how long you want the skirt to be):

Now flip your two pieces upside down, and rip down one of the old seams (where the arrow points) just enough so you can put the zipper in (but don't put it in yet)

Now put your two halves together, outsides in, and sew down the seams. Try it on- if you can't get into it, rip down your zipper seam a little farther.
From your leftover fabric cut 4 pieces in this shape:

The measurement of the longer edge should equal the measurement of the top of your skirt divided by four. The measurement of the shorter edge should be your waist measurement divided by 4.
Sew these pieces together into one long strip.

Now pin this strip to the top of your skirt so that the edges line up with the space you left for the zipper. Sew it down.
Now just put in the zipper and hem the top and the bottom, and you're done! If you need to add darts to make it fit properly, I'd do that by taking in one of the four seams that are already there.
OH, if you follow this the seams won't line up the way they do on mine though- you'll have seams in the front and back and down the sides. If your fabric is stretchy you could probly just turn it, which is what i did, but if your fabric doesn't give much it might hang funny if you do that.
I hope that makes sense! Let me know if you have any questions.