Actually I have this hunch that humans in general are easy, but I'm not arrogant enough to dare speak for the female half of the population.
It doesn't take much to gain our interest. Any old poster that features a woman with big guns (if you find a reason*to feature her half naked, toting some serious weaponry that could be a plus), will sway us in your favour. What brought forth this admittedly not to deep insight into human nature, I hear you ask?
Stumbling over the poster for the movie Jopog manura (My wife is a Gangster) did.
You gotta admit she's hot as hell. And sex sells, always!
Interestingly enough movie poster history lets one come to the conclusion that half naked muscular men have much the same effect on us. Hell, it might even be enough to prominently feature some bad-ass looking weapon, to get us all buttered up. Sex & Violence that is what men are interested in. If you can combine these two into one motive you have a winner.
*Fool! Who needs a reason long as she has a hot body**? **Heck, who needs a hot body long as she's half (or better yet bare) naked?
"When someone doesn't show up, the people who wait sometimes tell stories about what might have happened and come to half believe the desertion, the abduction, the accident. Worry is a way to pretend that you have knowledge or control over what you don't--and it surprises me, even in myself, how much we prefer ugly scenarios to the pure unknown. Perhaps fantasy is what you fill up maps with rather than saying that they too contain the unknown."— Rebecca Solnit