...get your bicycle tuned up. If you live in the northern hemisphere, your local bike shops are probably all but deserted right now. The small holiday sales rush they might have seen is definitely over, and business is as slow as can be. Right now they've got plenty of time to do a thorough tune up of your bike. You may not get a discount, and frankly, I never look for discounts from small local businesses when they're hurting anyway. But what you can count on from a bike shop in January is no service backlog to create delays. So why not give them your business now when your bike will have their undivided and careful expert attention?
A tuneup done on your bicycle now will have pretty good "shelf life." That is, there's little disadvantage to having your bike tuned up five months before you start riding it heavily as opposed to a week before you start riding. The tires will need to be checked and maybe pumped up again. But all the other adjustments will keep for quite a while.
If you ride only during part of the year, it's a much better idea to get your bicycle serviced now rather than wait until everyone else is thinking about getting back in the saddle again. While they all curse the delays caused by their lack of foresight, you'll be enjoying those glorious first great riding days of spring. And you'll help a local business in one of the leanest times of the year as well. And if you're one of the intrepid souls who ride year-round, this is still a good time for a tuneup. You definitely don't want to be stranded by a mechanical failure at this time of year.
Ride carefully out there!