Films have traditionally been marketed by following a four quadrant recipe. For example “this film” appeals to males under 24, females under 24 hour, or males and females over 24 etc. Of-course this way of marketing is extremely coarse and unrefined. Who in their right mind would believe that all men under the age of 24 like all the same films? Some boys like dolls, some boys like cars.
A much more accurate way of interacting with your audience is Seth Godins concept of forming tribes. A tribe is a group of people who have some special interest in common… computers, martial arts, dogs, music, gay rights, stamp collecting, politics, Christianity etc. Within each tribe there are many sub-tribes or extended families.
The key to identifying your movie audience lies with identifying the special interest tribes that exist in your particular story and filmmaking technique.