Coming up on my first winter, I'm worried I may be under-prepared. Is Deerclops guaranteed to spawn every winter? And does he spawn near you? If not does he move randomly or does he behave like the Hounds and seek you out?
Yes, the Deerclops spawns every winter, roaming the land looking for things to crush.
It does not seek the player actively unless it gets close, but it will always be announced by a growl and the ground shaking. If you stay out of its way you can make it pass, but it will not despawn until it's Summer again, so if you don't have the right equipment to fight it prepare yourself for a lot of running.
If you are getting followed by a Deerclops you can shake it off your back by making it fight other monsters (the Walruses are very effective at this), or you can make it fall asleep with the Pan Flute or the Sleep Darts. These are the only ways to make it sleep though, since it doesn't sleep at night, so it won't stop pursuing you if you're caught by the darkness.
Try to keep a good armor around, and a good weapon too if you plan to challenge it: it has a lot of HPs, a very high damage and a Sanity drain aura. If you fear you can't stand up to the challenge, you should have already learned what to do: RUN!
Other informations on the Deerclops can be found on the wiki.