Beyond checking a license, the conversation you have with a contractor before hiring them tells you almost as much as the paperwork does. A short list of direct questions, asked the same way to every bid you get, makes it much easier to compare contractors fairly and catch problems before they become your problem.
Start with scope and permits: ask exactly what work is included in the quote, and whether the job requires a permit. If it does, ask who is responsible for pulling it — it should almost always be the contractor, not you. A contractor who suggests skipping a required permit to save time or money is asking you to take on legal and safety risk that the permit process exists to catch, and it's one of the most common ways homeowners end up with problems that surface later during a home sale or insurance claim.
Ask about insurance specifically, not just licensing. A valid trade license and current general liability insurance are two different things, and for larger jobs you may also want to confirm workers' compensation coverage, which protects you if someone is injured on your property. Ask to see a certificate of insurance rather than taking a verbal confirmation — a legitimate, established contractor can usually produce one quickly.
Get the pricing structure in writing before work starts: flat rate versus time-and-materials, what happens if the job uncovers additional problems once work is underway, and what the payment schedule looks like. Be cautious of any contractor who asks for full payment upfront — a reasonable deposit is normal, but the bulk of payment tied to completed milestones protects both sides.
Ask about warranty coverage on both the labor and any materials or equipment installed, and get the specifics — how long, what it covers, and who to contact if something needs to be fixed under it. Manufacturer warranties on parts and equipment are usually separate from a contractor's own workmanship warranty, and it's worth understanding both before the job starts, not after something breaks.
Finally, ask for recent references or reviews specific to work similar to yours, and actually check them. A contractor with a long track record should have no problem pointing you to real customers or genuine review activity. Cross-reference what you hear against the license history and review data available on this site — years licensed, review volume, and rating together paint a much fuller picture than any single data point alone.