For many people, new pants need a little adjusting. If they fit the hips and thighs, they may be too big at the waist. You could just add a belt, but that usually leads to unflattering bunching at your midsection. Take in the waist yourself to get the perfect fit without spending extra money on tailoring. The best location to take pants in are the center back seam. Men's and women's pants can be taken in up to about 2 inches without affecting the overall fit.
Remove the belt loop at the center back with your seam ripper.
Take out 2 to 3 of stitching of the waistband facing with the seam ripper. Then remove stitching from the center seam almost down to the crotch.
On the inside of the pants, mark a line where you think the new seam should go. Starting at the top, draw a curve on each side with your fabric pencil eventually meeting your old seam. If you just want to take in the waist, start the line at the top and within an inch or two meet it to your original seam. Then pin the seam together.
Sew the waistband back together where you took out the seam.
Position the belt loop centered between the middle two belt loops on the center back waistband. Sew it back onto the pants in the new position.