Post a screenshot of your character as well as the scenerio you'd like to see your character in. This can either be a simple scene such as a simple pose or slashing a sword. Or it can be more complex like a small joke. Either way it has to be something I can realistically portray in a single image with minimal text.
How I determine who gets picked is by how interesting the scenario is as well as how possible(the more possible to pull off the more likely) as well as how fun it may be to draw. I may also pick more than one to do.