Men are fearful of packs of women; simply they can’t figure out how to infiltrate the swarm. Therefore you are most likely to attract the attention of a guy by either going out alone (but make sure you look happy about being alone, not bummed out about it) or in a group of three. When you are alone, you literally have no competition. A guy doesn’t have to worry if he is intruding an important conversation with friends or if he is bothering you. By showing up alone, you are quietly saying that you are open for business. In the case of a female threesome, your party is not only small enough to be non-intimidating by a guy, but the guy knows that when he steals you away, your friends can entertain each other, reducing reluctance from you to go along with it, as well as resistance from your friends since they have each other to hang with.