Smile... Women are smile-addicts. A few well-placed smiles, a happy attitude, some (non-erotic!) jokes here and there and you can win a woman's heart faster than a handsome tall guy, who is grumpy.
One reason why women react so positively to smiling and humor is probably that it shows that the man is not dangerous. It could very well be that many women want strong men, but, at the same time, are afraid of them. Smiling and being friendly compensates this fear.