Bring the water to a rolling boil, then lower the heat to a simmer, before adding the pasta. Ravioli is a stuffed pasta, which makes it more delicate and prone to bursting open in water that's boiling vigorously. The last thing you want is a plate of mushy, hollow ravioli served with its waterlogged stuffing. You can usually tell when ravioli are done cooking when they start floating, but it never hurts to "sacrifice" one for a taste test to be sure.