What does the phrase 'make the girls tick' mean?

The phrase is "what makes one tick"

what makes someone tick

Fig. something that motivates someone; something that makes someone behave in a certain way.

In your dating context it implies you should not just know the person superficially but also get to know what that person is interested in, what motivates them, what are their likes and dislikes - and that will help you have a better relationship.

I imagine the origin of the idiom will be from knowing the internal machinery which makes a clock tick.