Raise your body temperature by getting active. Move around on your motorcycle, one leg after the other, one arm and then the next. Take more frequent stops to warm up and move! Roll your arms and wrists around, even when stopped at traffic lights.
Make the most of your vehicle's in-built heating device: its engine. During short breaks, put your bare hands close to the engine (without touching it, of course!) to warm them up. Stopping for a few minutes? Place your gloves close to the engine, wedge them under the fairings or on top of the cylinders for a flat twin engine.
To warm up afterwards, place your hands near to a heat source (radiator), but never put your hands directly on it! The cold numbs: there's nothing worse than plunging frozen hands or feet into very hot water. You're sure to burn yourself. Immerse them slowly in luke-warm water and gradually increase the temperature.
At the end of a long winter journey, it can be tempting to speed up or skip a stop to get to your destination sooner. It's a fatal mistake! The last few miles are when you're most tired and least attentive and are therefore when most accidents occur.