If you have a skirt that doesn't fit quite right and is in need of just a minor alteration, you can do this fairly easily with a few sewing tools at home. Altering the waistband of a skirt doesn't take much time and will prevent you from having to retire a favorite garment due to poor fit.
Remove the waistband. When your skirt is too tight across the waist and hips you can change the size of the waist simply by using a seam ripper to remove the waistband. You can also remove the zipper, if present, to create a bit more extra room. To do this, just put the seam ripper into the stitches at the waistband of the skirt and pull the stitches out. Once the waistband has been removed, you can sew in some elastic. To do this, cut the elastic to the right size for your waist and run the elastic around the edge of the skirt where the original waistband was. Fold the top of the skirt over and using a sewing machine or by hand, sew the elastic in where the waistband used to be.
Add fabric. If you remove the waistband and realize that the skirt still requires significant alteration, you can add a piece of wedge-shaped fabric to your skirt to widen the waist even more. To do this, first release the seam in the center of the back of the skirt by at least 6 inches. Next,decide how large a piece of fabric you need. The easiest way to do this is to try on the skirt and use tracing paper to trace the opening you want to fill. Then transfer this drawing onto your fabric and cut it out, making sure to include a seam allowance of 3/4 inches. Now stitch the new piece onto the open seams of your skirt. You can do this by hand or with a sewing machine. To finish, reattach the waistband. If the waistband is too short you can add another piece of fabric to the back, or merely let out the center back seam if that is sufficient.
Reduce the darts. You can do this by using a seam ripper to pull out the stitches that are holding the darts (the folds of the skirt) together. If you reduce them, you should measure how much the waistband needs to be increased and divide that length equally between the darts. This will let you know how much of the dart to let out. For instance, if you have three darts on the skirt and you need an extra 3 inches of fabric on your waist, each of the darts (folds) will need to be reduced by 1 inch. Once you have pulled out the stitches holding the darts together, refold the darts but use 1 inch less fabric for each fold. Then, using a sewing machine or by hand, stitch the dart folds back together.