First, I'm thrilled for you that you are considering doing NaNo! I'm the Municipal Liason for my local region and have done NaNo every year.
I try to shoot for 2000 words a day. This lets me have "off" days (whether coming up short or brain freeze or whatever).
My first piece of advice: Don't fall behind. It's way harder to catch up than it is to start out ahead and maybe slip back toward your goal.
Second: I tell all the local WriMo's that the goal is getting words on the paper. It's a quickly written first draft, and will NOT be good. Strive for mediocrity. December and January is when you can work on fixing things.
Get in touch with your local Municipal Liason. We try to schedule "write-ins" where you go spend several hours as a group focusing on getting words down. It's amazing how much easier it gets when you have the support right there with you.
Planning: There are two different types of writers (roughly): Plotters and Pantsers (otherwise known as discovery writers). You need to figure out which you are. Plotters will have outlines and scene lists and a plan of what is going to happen before they start. That's me, and that's what I do in October. You can do all the planning you want ahead of time and it's not cheating.
If you're a discovery writer, then you will probably have a character in mind and plop them into a situation and see what happens. For those types, I encourage the writers to get to know the characters as much as possible. Character sheets, questionaires, those sorts of things. I find it helpful to do character interviews. That's where I sit in front if the keyboard, ask a question as me, then write an answer as the character. Conduct it like any other interview.
With the proper prep work, I spend two hours a day (give or take) and hit my 2000 words every day.
If you want to be "writing buddies" on the NaNo site, look me up:
I hope you go through with your story and best of luck!!!