How do you know it's love?
I have to comtemplate this... Imperative to the romance novel is knowing the signs, knowing how your character will react to the knowledge that he or she has fallen.
Sometimes, I have to make it up--like when my villain has fallen for the heroine...and showing, acting on that love means killing for her.
Sometimes, I can imagine it--like when my hero's best friend--Sean, married for three years to his high school sweetheart, witnesses the birth of his first child and suddenly knows... with the clarity of a perfect four carat diamond that even though he married his sweetheart because she was pregnant with a child they eventually lost, he can't live without this woman. She's his life.
Knowing you're in love might mean fighting as passionately as you make love. It might mean quiet nights of pillow talk and cuddling, or fear so stark, running seems the only reasonable option.
But the ultimate know is in his Kiss.
...i'm laughing my butt off right now, because this just came to me in a flash...
Inspired, seriously, isn't it? :D