I'd add that stuffing a rag in the air intake as well as the exhaust pipe also is good. The idea is to reduce air flowing in and out of the engine interior and leaving condensation. For the same reason, it's best to leave single cylinder engines on a compression stroke so both valves are closed. Also, it's better to remove the battery. It will freeze if it becomes discharged. Most batteries probably would survive a freeze. However, the risk is deciding to start the engine, finding a dead battery and putting on a charger without knowing the battery is frozen.
I believe that starting and running an engine once a month is better than storing one. It seems sort of strange to start a hand snow blower during the summer and a riding mower in the winter, but I do it.
