The easiest way is with a foam cover that holds onto the spigot with a cord.
This Amazon link illustrates a several types of covers. Order them NOW, before the winter – Local stores will run out of these, and they are so much easier to put on than wrapping the spigot with insulation, towels, etc.
If it is unusually cold, old timers would leave a small drip of water running, since moving water does not freeze. I would only do this in an extreme situation.
If you don’t cover the spigot, and it does freeze, you will have to have it repaired or replaced. this will cost a lot more than a cover. It is also a good idea to drain your hoses and bring them inside, or in a shed or garage, where they are shielded from the elements.