While your water or pasta is boiling, keep the water from boiling over simply by placing a wooden spoon across the boiling pot and this keeps the water from boiling over and making a mess over your oven.

Why this trick works?…

Because the bubble from the boiling water are filled with steam and if these bubbles touch something with the temperature less than 100 °C (212 °F) the steam will be condensed and will break the surface of the bubble.

The other reason is that the bubbles destabilise once touched by a dry wooden spoon and this cause breakage of the bubbles in the surface of the boiling water.

Note This:

While this trick works, at some point the wooden spoon will heat up to the point of the water temperature and this will cause the water to boil over even though the wooden spoon is across the pot.

At this point you can blow the surface of the boiling water, as your breath is lower than the temperature of the boiling water.

If you keep using the same wooden spoon over a pot of boiling water, it will warp from the moisture and heat. So be sure to keep a couple of spoons on rotation, or at the very least, keep an eye on your boiling water so the spoon doesn’t stay up there very long.