From NASA:
Baby, it's cold outside -- but you can still enjoy the best meteor shower of the year. The 2010 Geminid meteor shower promises to be lively, with realistic viewing rates of 50-80 meteors per hour and potential peaks reaching 120 meteors per hour. Anytime between Dec. 12-16 is a valid window for Geminid-watching, but the night of Dec. 13-14 is the anticipated peak.
From KingBee:
The later you stay up, or the earlier you get up, the better. I heard the best time is arounf 3a.m..
So if you are a brave, hearty, imsomniac camper with a good coat, this is the night for you!