I'm a fan of brainstorming techniques, and commonly use mind mapping as a means to rapidly outline a character, a scene or an essay.
What techniqes do you use and how do they work for you?
Following is a link to a public forum on Liberty Hall where I posted some examples. There are also links there to mind mapping sites, and to sources of mindmappingfreeware. You don't really need software to do this. You can do it on any piece of paper. I use mindmapping for work and for training people in brainstorming techniques.
Generally, right now, I just try to walk a few mental miles in the character's shoes. I suppose something like what an actor might do to 'get into character.'