TheLastRunaway said
My first question would be, Should I use a character sheet?
The simplest answer is, you should do anything that you think might help. Some writers do better when they have a plan (be that character sheets, story outlines, or sometimes even pictures and soundtracks for specific scenes). Others sorta play it by ear -- 'Seat of the pants' is the phrase people use, just flowing naturally from one plot point to the next.
It's counter-productive to speak in generalities, but
generally, most people wind up writing way, way more material than makes it into the final draft. Whether that's in the form of planning and outlines, or just deleted scenes -- you should expect to write lots and lots of extra stuff that isn't ultimately going to be used. So with that in mind, it's not like writing a sheet is a waste of your time. It can help you keep things organized, and that's usually helpful -- but not always. It might also make your characters too static, if you keep coming back to the same big pile 'o' facts.
I use a writing program that lets me keep several files open at once (
LSB), and one of the advantages is that it's super easy to keep notes on like a bunch of characters all at once. I don't really use it for 'character sheets' in the RP-sense, but it's nice to be able to keep active notes on whatever's happening in the narrative at the time. If I get an idea for something the character might be thinking, but not saying/doing yet, then I can put it in their file and pull it out later. That's what works for me -- your answer is probably going to be different.