Chemistry

Oooo la la

Nothing like the first stirrings of romance in the air. Whether it be a mutual spark or just strong feelings whenever that other person is in your vicinity. And when you fight those feelings...it's the verbal repartee that ensues. Oftentimes brutally honest and entertaining.

I love character dialogue. When the hero and heroine engage in verbal foreplay. Because that's where chemistry starts. Sparks. And ignites.
The two may be oh-so-hot in the bedroom, but if they can't hold a conversation that holds my attention...I don't really care.

Chemistry is the glue that binds the hero and heroine. So it's incredibly important to give them traits that spark off one another. Interests that may be diverse and polar opposites.

You can't have Jack and Jill walking the same path, holding hands, and whistling a tune. How boring is that? Too boring to even contemplate, quite honestly.

Don't be afraid to shake up the status quo. Throw in some conflict. Make your characters as human as possible. Make them fallible. They don't have to be perfect.
But, by God, they HAVE to have chemistry.