|To fit as you sew your pants use the following order:
Stitch back crotch seam to within about 3" of the inseam. Insert your fly-front zipper (if pattern has a back zipper insert it) - again crotch seam should be stitched to within about 3" of the inseam.
Pin in darts, inseams, outseams - all with seam allowances to the outside to allow adjustment without removing pants.
Try on the pants with elastic around your waist to hold the pants up. I adjust the inseam first, then the outseam, check all darts (is location correct? is depth correct?).
Stitch the inseam, darts, remaining crotch seam, then outseam (I sometimes try them on again before sewing outseam). Then I would put them on again with the elastic around my waist and mark the waistline seam (my teenage DS is a big help here - anyone who can run a chalk wheel under a piece of elastic can help you in the back - but if you're alone that's still okay).
Trim the waistline seam evenly to whatever seam allowance you will use. Apply waistband. I usually cut an extra long waistband since I can cut off whatever I don't need. If you have a helper you can try on the waist band when you have your pants on and have your helper mark CB, dart locations, side seams, CF for you. I never just use the pattern piece given since I know I have to make adjustments.
If the pant is too large in the waist it should generally be taken in at the side seams. Remember that a deeper dart points to a bigger bump, a shallow dart points to a flatter bump. So unless your waist is small and your derriere is rounder than average you should not be deepening your darts to reduce the size of the waist. But I am all for pinning darts in (to the outside) to allow fine tuning before sewing since it's unlikely that you are shaped exactly like the pattern. To deepen darts just redraw the lines - darts can also be shaped to mirror your shape. If you pin-fit the darts on you, you can just chalk mark the new dart legs on the inside of the garment.