The tight, non-negotiable deadline and the challenging minimum word count are the secrets of NaNoWriMo's genius, because they focus the mind remarkably well.
If you feel any muscle tightness while you're warming up, stop jogging for a moment and stretch out the tight area (but don't count this stretching time as part of your 10-minute minimum).
Generally speaking, writing fast code means keeping memory allocations to a minimum, writing tight code, and avoiding certain language and programming idioms that can subtly cripple performance.