Okay, hope this makes sense...
I typically make a 4" bow, using 18" of 7/8" ribbon. Satin makes it less poofy, grosgrain can be stiffer and poofier. (walmart has cheap ribbon, dollar store has the clips, all you need is hot glue...)
1. Cut and heat seal your ends.
2. Hold one end in your left hand (if you're right handed), the end pointed down, and wrap the ribbon around your hand and over the top, letting it hang over to the left. Put the end in your hand on top of the other piece. Wrap the ribbon around again, but thread the end under the other layers in your hand. You should have two loops and and end on either side of your palm.
3. Even out your loops, and pinch the middle. Wrap it with some wire to hold it, and then floof it out to the desired poofiness.
4. Glue it to your hairclip in the middle, then wrap some extra ribbon around the middle to cover the wire, and glue the ends of that to the underside of your clip.
Done! The looping method is the hardest to describe, but you could adjust it for your own style. Just make sure you've got even loopage around your hand. You don't want the ribbon to just be coiled or folded, or the bow will be FLAT. (That could be another look, though!)
The thinner the ribbon, the shorter you need, and the smaller the bow. Same goes the other way. I tie a knot in the little piece I use for the middle so it stands out. Could be flat though. Or thinner. You can clip them onto a fabric head wrap/band to change the look every time. My daughter wears them on pigtails and braids...
I know the ribbon in the pics changed, but I already had some in various stages of doneness...
Hope this helps!