Use a Wooden Spoon to avoid from Boiling Over

An unwatched pot can go from boiling to overflowing pretty quickly.

Here is the simplest trick to avoid this by putting a wooden spoon over the top of the pot.
If it starts to boil up to the height of spoon then the spoon will pop the bubbles and keep it from boiling over as quickly, meaning you have more time to get back and turn the heat down.