Summarize:

There are two ways to sew a hem: by hand or with a sewing machine. While the latter is obviously faster, the former allows you to sew a hem without many tools. If you can, set up your sewing machine for your hem; use a straight stitch for a double-fold hem. You're almost done! To finish off your hem, you need to iron it so it lays down flat. If your fabric can handle it, use a bit of steam to help with the ironing process. When you're done ironing, turn your fabric right-side-out, and enjoy your newly completed hem.
Decide how you will sew your hem. Iron the hem.