Most warm water species are sluggish in the winter for 3 simple reasons. Lack of oxygen, lack of heat and lack of food. It has been my experience that if you eliminate these "lack ofs" then you will catch fish consistently. I have had days in the winter with over 20 carp to the bank in one session, in December...when many people said they stopped biting when the water went below 35 degrees. Then just to prove a point I did it in January and February as well...this last winter at one point after shoveling some 3 feet of snow off the swim.
The key in my mind is, as has been stated finding the fish. Using your head and tracking the heat. Fish will follow warm breezes, the sun, inflows of warmer water etc.
The second and third part you can have more control over. Oxygen for instance you can help by keeping the snow cleared off your chosen swim, if ice fishing. Snow covering the ice reduces the plants and algae from creating oxygen. Since decomposition and metabolism continue normally the oxygen levels will continue to drop but not be replenished if the ice is covered. Finding clear ice could be beneficial in this regard as well. Keeping it clear could produce higher oxygen levels over all and possibly stir fish movement a bit.
Food is the simplest to control really. If you can find a good spot that holds fish..how many of you have tried keeping small particle like bread crumb or oats going into your holes? Something to think about. I have underwater footage, albeit bad quality atm, of a chummed/groundbaited area for carp. What is neat about this is after a few moments of the ground bait being there the shiners/chub/suckers moved in to have a feed. About 10 minutes after that the Bass moved in to eat them...food for thought that is. If you give the small baitfish a reason to be in your swim, the predators will have a reason to be there as well. It is the same reason old timers poke holes in a clear soda bottle, fill it with water, tie it to a string, toss in a few shiners and let it dangle through a hole hear their ice hole..
Anyway it is way to early for me to be talking serious about anything lol. Off to the airport soon
to drop Nate off. Hopefully my early ramblings help a bit