In the winter, you will want to only fill your feeder half-full, due to a decrease in the number of birds that will likely be visiting your feeder. You will want to change the nectar weekly, rather then every 3-4 days, to ensure that the nectar has not spoiled. A spoiled food source will drive the birds away and it will be hard to get the birds to once again trust your food supply.
In order to prevent the nectar from freezing, you may want to bring the feeder in at night. This will help ensure that nectar solution will remain liquefied when the feeder is once again placed outside and therefore the birds will be able to get a drink of the nectar whenever they need one.
In very cold weather, many people choose to alternate feeders by having two of them. This allows the warm one to be put out at mid-day and the cold one can be brought in the house.
There are many other alternative methods to help ensure that the nectar solution stays warm or to keep snow off of the feeder. These include the following: heat lamps, electric pipe wrap, and other creative solutions that people have developed.
Lastly, your winter feeder should include a perch; this will allow the bird to feed without expending much energy as well as enabling you to have a close-up view for observation and photography.