Okay, this is optional, but it's fun and can help generate interaction: Storylines.
Basically, you write a list of characters from the fandom your character is from that they would have a relationship with. Then you try and fill them with other played characters. Some of them follow the fandom, like The Doctor is Rose's THE DOCTOR and she is his THE ROSE. Others don't, e.g Gabriel is The Doctor's SARAH JANE SMITH. You don't need to know the fandom to fill a storyline; that's why the descriptions are there. I've written out mine so you can see what I mean. Let me know if you want to fill any of my storylines!