I usually approach my local quilt shop owner and ask if she'd carry some of mine if I make a sample for her to sell them. Works for me as I'm not particularly interested in a big job.
There is more to marketing your pattern than just the design work. You will need to test the pattern, either on your own or by having a friend, guild member, or another person make the quilt by the instructions you've written.
If your pattern sells in the shop for, say, $8, you'll be selling it to them for $4 or even less.
If there is a middle man seller to the shops (catalog company?), you'll be selling for even less.
Remember you have to print the pattern, put it in an envelope, and have a color photo of the finished product on the front.
There really are very few who are making much money at this. It's much more a "passion" thing to do. :-)
Jan in VA