We had a shower curtain liner, and wanted a really simple cloth shower curtain to go over it. After reading a few posts on DIYing a shower curtain, I thought it would be worth a try.
Here's what we did:
1 - Grab your liner and take the clips out. You will have to match up the shower curtain holes with the liner holes. At this stage, our shower curtain had also been hemmed on the top - so there were no holes, loops or grommets, just a 2 inch top hem to work with.
2 - Match up the holes. It won't quite match up - the curtain isn't quite as long as a regular shower curtain so for some you will have to skip a hole. Meaning, if you pulled the shower curtain out fully, it would bunch up the liner a little (but we didn't care, you never really need as much length as the shower curtain gives you).
3 - Poke the holes. This seems like a crazy technique.... but so far it's working fine! You might want to do something fancier - use a grommet, sew around the hole etc. But once we did one and realized you couldn't even see the hole when we hung it up, we didn't care.
4 - Thread curtain onto clips as per usual.
5 - Hang and enjoy your $2.50 shower curtain! (Oh, we also made a nice thick hem at the bottom of the shower curtain using the same iron-on method that used to trim up our other curtains).