I make my "resolutions" during Rosh Hashana and the High Holy Days. For me, the secular New Year is a fun reason to party. I personally don't make any resolutions around then, but I do party like it's 1999.
I never really *wait* around for the new year to make changes but I do make a coupe resolutions. I generally try whenever I feel the change is made but I do think the fresh start of a new year is always extra motivation to get more serious about something. I lost 40 lbs this year and unfortunately put 20 of it on while out of work and just being lazy. Right now I'm working on maintaining since I am trying to find the time to make healthier meals, but of course I plan to move on to weight loss mode soon. Obviously the most convenient time is right after the holidays.