Winterize your coop
I'm going to send you to last winters posts for the first 2 tips. The first one is insulating the coop permanently. We used rolls of insulation in our largest Guinea coop. It was simple to attach to the ceiling using a staple gun and really made a difference in the temperature and moisture level inside the coop.
The second tip is Blocking Winter Drafts temporarily in the coop. We used old towels and blankets to block drafts for the worst of the winter days. These are easily removed when the weather warms up.
Be careful with equipment
Snow shovels are more brittle in cold weather. Frozen buckets can split when dropped. Water bowls can crack when the water expands as it freezes. Empty excess bowls and buckets, preferably washing and storing till warmer weather hits.
Feeding more carbohydrates
Feed like cracked corn, scratch, bread etc are full of carbohydrates. In the summer this should be limited, but an extra handful of corn thrown to the flock in the winter can help them warm themselves up. Lots of flock owners believe in adding corn to their chickens diets in the winter.....some disagree with this, as always do what's right for your flock.
Some chickens molt in winter. I have 2 Marans hens and 1 Silkie hen molting right now. I can't seem to convince them that it's the wrong season for it, so instead I've put saddles on them. Totally not the purpose of saddles, but I believe it adds a layer of warmth across their backs. Can't hurt right?
A thin layer of Vaseline rubbed into combs and wattles can help prevent frostbite in the winter. Some chickens seem to love the extra attention too!
Take care of yourself
Hats, glove, winter boots, heavy coats and even snow suit style coveralls go a long way towards keeping you comfortable while you take care of your flock. One of my favorite things is do is to put rubber gloves on top of a pair of knit gloves. This traps the heat in and keeps my hands from getting wet when I'm pulling ice chunks out of water bowls and cleaning snowy wet food out of feeders.
These are just a few of the things that I do special for my flock in the winter. What do you do differently when it's cold out?