It's not the professional way, but I turn my clothes inside out first, spray a good bit of starch on the seam, and iron it, holding the iron in one place for a few seconds at a time. It takes time and patience but it works for me. After it has mostly smoothed out turn the pants right side out and do the same. Ironing inside out first eliminates most of the ironing time so you don't have to cause any undue damage to the outside. The starch works wonders. If you are conserned about harming the outside of the pants, spray with starch and lay a thin towel over it before ironing.
Depending on the garmet, it could take a couple of tries between washes for the crease to fully flatten out to where you don't know it's there anymore. Washing it after ironing will help with the process.
As far as adding any material on the hem, since you can't double it under due to being denim, I'd just serge or zig zag the end and sew around it. There is also a fusible tape that you can use to bind the material together if you don't want a stitch line. You can get it a Wal-mart.
