Despite chickens being pretty easy to keep on the whole, moulting can be a time where they really appreciate a little extra help. All birds are different - some will lose a few feathers at a time and some, like my Cream Legbar in the photo, will end up like a bald pin cushion!
It can be quite worrying for new owners to head out in the morning to find a semi-naked chicken wandering around! Moulting is a completely natural process and the hens are just replacing their worn out summer feathers with new fluffy feathers to insulate their little bodies from the winter cold. If you have hens in their first year, they shouldn't moult this year - they are usually about 16-18 months when they go through their first moult which is triggered by shorter daylight hours.
It's not advisable to handle your hens when they are going through a moult as new pin feathers can be pretty painful when touched. If your hens haven't started moulting yet (they could start from any time now) it's a good idea to check them over for any mites or parasites now and treat them accordingly.
I also like to worm my hens at this time of year to ensure that they are as healthy as possible as they enter the moult. A tonic can be beneficial, and I love to feed my hens a treat of protein rich sunflower hearts when they are moulting. Steer clear of dried mealworms through - DEFRA banned the feeding of dried mealworms in 2014 as imported mealworms are often raised in very unsanitary conditions. Live mealworms are fine though - your chickens will love a mealworm party and will also appreciate the extra protein.