Something to consider before heading to Newport is to become a member of the Preservation Society Of Newport County. Becoming a member helps to support the preservation of the various mansions; it also provides you with some benefits that will be useful during your trip. As a member, you get free admission into the various mansions. In addition, you also get front of line privileges - which is great when the crowds are in full force.
And another thing, your membership donation is tax deductible.