Obviously first you have to get something written. Make it original and well plotted, not the half-hearted tripe that's popular nowadays *cough* Twilight *cough*.
Then you have to contact an agent, and if they like your work then hopefully they will contact a publisher who will hopefully get it...
Well, I don't read much romance, but I really liked these:
Junk - Melvin Burgess. Tar and Gemma are in love. Tar has reasons for running away from home that run deep and sour, whereas Gemma, with her middle-class roots firmly on show, has a deep-rooted lust for adventure. Together they explore...