I know this one is pretty obvious, but I went a long time simply folding up the raw edge of what I wanted to hem and then sewing it. This winds up with a lot of fraying and looks icky, so I just wanted to put this tutorial out for the beginners!
Step 1: Iron the raw edge up about 1/4 inch all the way around where you want to hem.
Step 3: Stitch along the hem - sorry, I forgot to take a picture of the end. But it's pretty obvious...
That's it, you're done!