There are a million tips for riding a bike safely and especially through winter, but the biggest lifesaver for me has been to regard everyone else on the road as a retard.
Learning how to interpret other vehicle's 'body language' is a priceless skill to keep it rubber side down.
A few other important things:
Always maintain a decent distance between you and the vehicle in front - imagine they will slam their brakes on at any moment, and give yourself enough distance to react and stop yourself safely.
When riding in the wet/cold, apply BOTH brakes progressively, don't ever snatch at the brake or you'll lose the front end and go down like a sack of potatoes!
If you find yourself going into a corner too hot then look at the point where you want to go and lean smoothly into it; don't slam the brakes on as you'll stand the bike up and carry on in a straight line into the nearest telegraph pole/oncoming car/kerb/armco etc. Target fixation is surprisingly easy to fall victim to so always keep your eye on where you want to go. You'll get away with gently applying the rear brake round a corner - you want maximum grip from the front wheel.
As for maintenance, the biggest issue you'll find during the winter is your chain getting covered in crap. Keep it clean and lubed up. To protect the exposed parts of the bike from salt etc, get a can of ACF50 and apply it with a cloth, obviously keep it away from the brakes
Happy biking
