To create a band with a clean edge, fold the fabric strip in half lengthwise with the right side out. Press (or iron). We'll be using that pressed (or ironed) line as a guide for the next step.
Open the fabric strip, and place it with the wrong (or back) side up. Using the pressed center line as a guide, fold each edge almost to the center. Press.
Fold the band in half again (hot-dog ways) and press. You shouldn't be able to see any raw edges, and the pretty part of the fabric, the right side, is the only part showing. From here, your pattern will usually direct you to how to use the clean edge band.