I'm not sure my advice will help but I'll try. I'm finishing up a manuscript and what I have found is that after first seeing the character in my head, I list the physical attributes first, followed by the personality, demeanor etc, and I follow that up with the connections/relationships they'll have with the other characters. I even list them by age, category etc. Maybe it's too overkill and not "creative" enough but I find that having that list, as I'm writing I find more and more details that bring them to life and I add it to the list. Because for me I get to a point where maybe so and so's age needs to be accurate so I have to refer back to my "list" and even for trying to put things into time perspective etc. I think I'm rambling a bit and may not even be giving what you are asking but I swear I tried... :-)
Oh and another maybe too obvious tip but I keep a notebook beside my laptop where I do most of my writing and have my characters etc on that and add to it. I also care those little mini notepads that could fit in your back pocket around because you never know when an idea might pop up. I'm looking thru mine now and I have random things written down like songs that I think sound good and fit the theme of the chapter, history channel, dartmoor, just random things I hear or see that could be researched for content.
Glad I could help. I admire what you're trying to do. As I write my "novel" I see everything as a movie in my head. So I wish I had a talent or an education on script writing. I actually looked into a college in NY for that about 13 yrs ago when I graduated from high school but never quite made it there. You have youth on your side for sure and I wish you all the best!
thanks this helps more than you think! =]