Initially it would be mutual physical attraction and chemistry.
Without those two things I'm not likely to ask a woman out. Once you get to know someone you want to make sure you share the same values, want the same things for a marriage, naturally agree on how to obtain those things, and last but not least there is a mutual love and desire for one another.
Everything (begins) with the initial attraction. It's been said:
"Men fall in love with their eyes and women fall in love with their ears. However with age comes wisdom. Men learn everything that glitters is not gold and women learn that actions speak louder than words!"
Like attracts like in the long-term and opposites attract divorce attorneys! :)