Another tool I've added to my NaNoWriMo Prep Chest is a character list.
This should be something you can add to, but basically just a rundown of the characters you hope to include in your novel. Give each a one or two sentence description, who they are, how they relate to different characters. Sometimes I include a line of dialogue or catch phrase. Dialogue helps to make the character immediately full in my mind.
I also add labels, just to remember who's who, when my brain gets all mushy (which it always does!) Here are the labels I use:
PR - protagonist
AN - antagonist
MA - main character (not the protagonist in this case. Just characters who play a major role but are not PR or AN.
SC - secondary character
You can further group your characters as I've done in the following example if you like. This is a fairly complete example, as I have a pretty thorough outline and several chapters already completed for this book, but I'm starting a fresh Character List for my NaNoWriMo novel this week.
Character List – FINDING HOPE
Tessa (PR) – Main Character. Tough, independent, speaks her mind. "I'm hear, aren't I?"
Tessa’s Dad (SC) – A hermit since his youngest daughter died.
Tessa’s Mom (SC)– Gail/Abigail, left shortly after daughter died. Very "together".
Corey (SC) – Tessa’s younger sister, who died when she was six.
Shawn (SC) – Gail’s new husband. Bossy, a natural leader.
Hope (SC)– Gail and Shawn’s six year old daughter. Tessa’s half-sister. Tough. Speaks her mind. "What do you want?"
Brie (MA)– Tessa’s closest school friend, who she teamed up with in LOSING FAITH. Is willing to do what it takes to help her friends. Her sister Faith died a year ago.
Alis (MA)– Brie’s boyfriend. Conflicted but sweet. His sister Reena is in a mental hospital since she was responsible for killing Brie’s sister Faith a year ago.
Trev (MA)– English classmate of Tessa’s. Shy, a little nerdy, but good-looking.
Cami (SC)– English classmate, very academic, who has a crush on Trev.
Mark (SC)– Trev’s bandmate who looks a lot more streetwise than Trev.
Vi Masterson (AN)– Friend of Gail and Hope, but a thorn in Shawn’s side. Irresponsible but good-hearted.
Diane Masterson (SC)– Vi’s mother, who works for Shawn.
This is just an example. If you do anything to keep your characters straight, I'd love to hear of different methods of doing this. This is fairly basic, but it works for me.