I've been flying a lot recently and always do through the winter. Some of my tips would be:
- Fill up the tank after flying. Full tanks get less condensation in them.
- Clean the windscreen well before every sortie. Flying into a low sun with a dirty windscreen is very difficult - especially if there is poor visibility anyway.
- If you will be landing into sun late in the day you might want to have second thoughts about departing!
- Enough has been said about ice / frost on the airframe.
- If on grass it will be wet - allow for the longer landing distance.
- If muddy at the end of the day, and frost is expected, do you really want to give it a good wash and fill all the hinges and other orifices with water?