Check a quote before you sign it
Thirty seconds on the paperwork basics that predict most of the horror stories: deposit size, contract, registration. It won't tell you if the price is fair. For that, get three quotes.
Paperwork check 30 seconds
Rules of thumb behind this: deposits over a third of the total are outside normal practice; New Jersey requires home improvement contracts over $500 to be in writing; registration is mandatory (check any number here); and legitimate trades don't sell door to door or demand cash. Verify anything surprising with the state registry.