Doing a waist/seat is one of my favorite alterations to do. It's pretty quick, and I feel like I accomplish a lot. Measure the markings to see how much the pants need to go in. These pants need to go in 2 1/2".
Next, take off the belt loop.
Unpick the inside of the waistband right at the center back seam so that the band can be lifted up. (Unpick the stitching where my finger is.)
This is what it should look like when you fold the waistband up.
Lay out the pants with the seam allowance pulled out.Mark along the waistband, half of how much you need to take it. My full amount was 2 1/2" so my mark is 1 1/4" in.Make sure you sort of follow the curve at the bottom so there will still be room to move in the pants.
Lay it flat and pin along the marked line.
Sew on the marked line.Unpick the previous seam.This is what it should look like when it's opened.Cut the seam allowance down to be 1 1/2" to 2".Make sure that you tuck in the top corners when you iron so that the corners won't show when the waistband is closed.To close the waistband, stitch in the ditch about four inches across over the back seam. I don't have a good picture of myself doing this. Sorry!
Here's the result after the chalk has all been ironed off. You can't even seen the stitching. I decided not to put the belt loop back on because the two back belt loops are close enough now.