Keep your body core warm and your extremities will remain warm.
Not necessarily... If like me you suffer from pretty poor circulation, this is total crap. I have to work very hard to keep my feet, my ears, my fingers and sometimes my nose warm!
Anyway, I used to think that people were crazy spending a load of money on biking specific clothing just to ride their bike through the winter...
And for the most part I still do, but there are a couple of absolute essentials in my book, that without them winter riding can become a cold, wet and miserable experience.
- A pair of Goretex waterproof riding boots (I use Shimano MW80) will keep your feet warm and dry through just about anything, which to me is about the most important thing as I hate cold, wet feet!
- Knee/Leg Warmers (I use Endura FS260 leg warmers) cos if like me, you don't like wearing full tights, and like wearing baggies, these will keep your legs warm and pretty dry through most things. Also they're only about £20 or so.
Other than that, there are a few other bits and pieces I'd use too. A pair of warm gloves will be needed if you're riding sub zero conditions really, though hunt around and you can find them for bargain prices (like £10 or less!). I found a Thermal headband (again, under £10) is brilliant for keeping your ears warm in cold conditions, but still allowing your head to breathe whilst you sweat. Wear lots of layers, rather than a couple of thick ones, and use a Camelbak (or similar) that you can carry a bit in so you can take layers off and stuff em in your bag if needed.
And when it comes to your bike, as mentioned before Mud guards (like the crud catchers) are worth their weight in gold. Who cares what they look like when your arse stays dry! Winter tyres (I prefer the Bontrager Mud X in 2" size) are a worthwhile investment too if you ride anywhere particularly muddy. But if your bike has fairly knobbly tyres on already, they'll be ok.