Here's "4 holiday deliverability tips to get your emails delivered every time" from Sam McNeil from WhatCounts. Solid advice.
Allow me to add a fifth: Now is not the time to experiment. Don't dig out that old list, triple your volume or decide to warm up a new IP address in the middle of the season, if you can help it. As WhatCounts suggests in tip #3, some things are better addressed before you get here.
Or, to put it another way, now is not the time to do something that might blow up your sending reputation.
ISP representatives are getting overwhelmed for requests for remediation and have holiday vacations planned, both leading to slow responses. And enough of them are probably tired of people asking for special favors, especially when not really warranted (can you unblock my mail that has really bad stats?), that This Is Not The Time For Funny Stuff. The less your success relies on a human's personal intervention at an ISP, the better off you are.