I know what January's experiment will be: reducing clutter in the kitchen.
We've started. The kitchen table is the hardest target. We use it everyday for so many different activities. The surface fills up quickly: laptops, power cords, mice, books, plates, glasses. We're developing the habit of clearing it every night, keeping only the lamp, the power hub, and a bowl full of fruit. Everything else goes into cubbyholes or shelves.
Corollary: Doing one thing at a time, although it's hard to avoid the temptation to work while eating lunch or to read through dinner.
The kitchen sink is a good target, too. We used to leave dishes there while waiting for the dishwasher to finish, and sometimes if we didn't have the time to empty the dishwasher. It wasn't a bad system - we cleared the dishes before they got crusty - but still, a single dish acted as a nucleus that attracted other dirty dishes, even when the dishwasher was empty and ready for another batch. Now we make a point of emptying the dishwasher before meals, filling it up as much as possible, and washing dishes by hand if needed. W- is looking into fixing the top drawer of the dishwasher so that we can streamline this too.
I'm not going to make any grand year-long resolutions. One experiment at a time, one small and concrete change each month - that's enough.