I got this off of the TV a couple of months ago and keep meaning to share. It may be common knowledge, I dunno but I just learned it and it's too cool.
You know how pasta, potatoes, rice, basically anything starch-y tends to boil over on the stove? Just add a splash of Extra Virgin Olive Oil to the water. It stops it from happening. Seriously just a teeny amount like probably 1tsp or less. Works like a charm.