November is not a big deal to me... I live in Canada so Thanksgiving has already passed. In December though, I go home for the holidays (I normally live in a student residence on my campus in another city). It was really hard last year because my house is always full of food... not junk, but things like cheese and nice bread and muffins and fruit juice. Basically my strategy is to stay out of the kitcken as much as possible.

Another issue is that I go out and socialize with friends at restaurants, in bars and at people's houses. All the parties and get-togethers involve alcohol and junk food. My strategy for this is to plan some fun exercise-based get togethers like ice skating and stuff like that, and to exercise on my own too, to keep my motivation up.
Last year I came out of December with minimal damage: a 1 lb gain overall. Hopefully I can make it a loss this year!