Through a fairly straightforward set of steps, you can make a skirt out of a favorite old pair of pants, getting use out of them even if there's a hole in the bum or a few rips in the knees. The process is fairly similar to making bellbottoms. Since dealing with the waist can be a bit tricky when sewing a skirt, this is a nice project for someone just starting to sew, and if the pants fit, you can be fairly sure your finished product will fit you as well.
The process is as follows:
- Decide how full and how long you want your skirt to be.
- Acquire a yard or two of fabric.
- Slit the pants along the seams. The only tricky part is the crotch: There's some extra fabric at the inseam, so cut the seam above it and trim so that the fabric lies flat. You're also liable to be limited by zipper/button hardware here in terms of how high this slit goes, so take that into account when you're figuring out the height of the others--I'd recommend making them all the same size for simplicity's sake. If your pants don't have zippers or pockets or other things constraining the height for these slits, their exact placement is a matter of taste. Think about what part of you the fabric should flow out from. Hips? Knees? Halfway in between? Just leave at least 3 inches or so of space from the top of the slit to the waistband, so that the garment retains a bit of the original structure around the waist.
- If you want a fuller skirt, I'd recommend cutting each resulting section in half after that.
- Cut the pants to the length you want your skirt, allowing for a hem.
- Optionally, taper each section of the pants into a triangle (this is for aesthetic purposes only).
- Cut the extra fabric into wedges to fill the slits (the wider the wedges, the more full the skirt--45 degrees per panel with 8 panels will give you a full-circle skirt). You may want to do some measuring and make a template out of newspaper. It will probably look best if you also round out the bottom edges, but it's not necessary if you're not comfortable sewing anything but straight lines.
- Using a sewing machine (or a needle/thread if you're insane and have too much free time), attach the panels of fabric to the slits in the pants. I recommend pinning the fabric together before sewing. Make sure to use two lines of stitches whenever dealing with the edge of the fabric as protection against unravelling.
- Trim any excess fabric, hem the bottom edge (ironing helps), and you're done!
Some fashion-oriented skirts made from blue jeans use fabric from the lower legs for the inserts, eliminating the need for finding other fabric. They may also leave some raw edges of the denim exposed and leave much of the inseam intact, folding it over and trimming it to reduce the bulk but leaving the formerly-crotch-following curve sewn in place to emphasize the DIY nature of the garment. The look has enjoyed some popularity recently, and it's probably what most people will have in mind when you tell them you turned a broken pair of pants into a skirt. | 
