Since romance is a strong part of the books I am currently writing, I thought I'd make a list about the crucial elements of the Love plot, as described in "20 Master Plots." So here goes.
1. Love plots are character plots, and the writer must help the reader strongly identify with the main character and project herself into them.
2. You've heard of boy meets girl, boy loses girl, boy gets girl back? In essence, this plot structure is correct because romance is largely a story of frustration. In other words, something or someone always gets in the way of the character's budding romance.
3. "Happily ever after" is a must if you want to cater to mainstream readers. Literary writers can get away with tragedies, but if you want to make money, stick with happily ever after.
4. "We never feel so alive as when we are emotionally aroused." In other words, powerful, romantic prose requires the depiction of sincere emotions, not fake, over-the-top sentimentality. "Don't just talk about love," show your reader all its various emotions--fear, attraction, disappointment, etc.--as required by your plot.
5. Make sure that when your lovers finally find love, that they have earned it. Love is not a gift, it's the greatest reward to the severest test.
And finally (this is my own advice), make sure you, the author, truly respect this genre. A reader will recognize a phony in a heart beat.