Gapping WaistbandA gapping waistband occurs when the wearer has a waist that is smaller than their pants while the hip area fits fine. The waistband can be taken in by placing darts on either side of the back seam. If the amount to be taken in is two inches or more, I have found that it looks better to put in two smaller darts on each side instead of one large one. For this alteration, it is very helpful to have a second person to help you with pinning and adjusting the fit. To make pinning easier, put the pants on inside out and pinch out the excess fabric with pins. Try to hide the ending point of the dart underneath the back pockets, if you can. Before basting, even out the darts and make sure that they are the same distance from the center, are the same size, and point in the same direction. Baste in place with a long stitch, making sure that the pockets do not catch in the seam. Test the fit and adjust the darts accordingly. When you are happy with the fit, sew in a permanent seam. For comfort, press the fold of the darts toward the center and at the top, tack in place with a few hand stitches.
Fullness in the Thigh/Lower Leg AreaAs a person with an apple shape, I have had this problem crop up in the past where pants that fit around my midsection end up being too roomy in the leg area. It is easy to fix this by taking out some volume in the side seams. Depending on the pant style, you can take out room in either the inside seams, the outside seams, or in both. If you are working with pants that have a flat felled seam (common on jeans) on the outside or set in pockets, take up the inner side seams instead. The only trick is here is figuring out where to start the taper because if you start too close to the hip, it can cause drag lines across the midsection or upper thigh. Again, put your pants on inside out and pin out the excess fabric until you are happy with the fit. Try sitting down and walking to see how the fabric moves on you before basting in the new seam. When basting/sewing the new side seam, taper the seam very gradually in the beginning so that the transition is not glaringly obvious. When you are ready to put in your finished seams, open out the bottom hems enough to allow sewing of the new seams and trim any excess fabric from the seam allowances. Sew the final seams and finish the raw edges with a serger or zig-zag stitch. Press the hem in place and sew down to finish.
Reduce Width of Pant Leg at the BottomThere is a style of pant that has a very wide leg which is flattering on some and less so on others. Again, this is a fairly simple adjustment to make. Follow the instructions as noted above, starting the taper at the knee or slightly above. Be careful to taper the fabric proportionately so that it looks natural depending on the look you are going for.
I hope this has been helpful in your quest for better fitting pants.