With the introduction of the DLC update (Patch 1.29) Freemode Events and Rockstar Editor for GTA 5 you can across Los Santos and unlock 12 special characters and then you can enter the Director Mode of open-world game as an actor.
GTA 5: All Special Character Locations with Maps
The special characters are mostly quirky individuals who stand around conspicuously in the neighborhood. To unlock the characters for the director mode, it is sufficient to approach them. It then starts a brief conversation and you get a message about the activation on the bottom left of the screen.
Achievement "Human of Los Santos"
Once you have unlocked all the special characters and with one of them enter to the Director Mode, you will receive the achievement or trophy "Human of Los Santos".