You can reduce the risk of theft by parking off road in your rideway or garage. Most insurers will offer a discount if you do so. Your postcode area where you live and how safe your bike is during the night, will effect your premium value on most polices.
It's a common misconception that having fully comprehensive insurance means you can ride any motorbike. Unless your insurance states you are allowed to ride other motorcycles do not take the risk, no matter what the circunstances. If you are unsure and your documents are unclear, ring your insurance company to find out.
One way to save money on your motorcycle insurance, especially if you are a young rider, is to ride a cheaper motorbike with a smaller engine.