Check to see if the dealer possess all of the appropriate licensing for installing HVAC equipment in your state and local area.
Ask how long they have been in business; if they offer 24/7 service, financing, or accept credit cards.
Ask the steps they will take to install your equipment. A proper installation will follow the 3-part process listed above.
A dealer coming into your home should do more than just inspect your existing system. Follow them around to see if they are checking air flow, inspecting the duct system, making note of the windows and the direction your home faces, etc.
Be wary of anyone who shoots you an estimate on the back of a business card after being in your home for a few minutes, or even over the phone.
A knowledgeable dealer that has your best interest in mind will ask about your experiences in the home; how long you have lived there, how long you plan to stay, if you have pets, allergies, smokers, hot and cold spots, noise, etc.
A dealer with the tools to address these problems will offer viable solutions such as air cleaners, zoning equipment, programmable thermostats, humidifiers, variable speed and two-stage technology, etc. If they do not offer these solutions, they may not be the right dealer for you!
It takes more time to complete an installation when done correctly. Expect to pay more for comprehensive service, but much less in the long run for your system's performance and maintenance.
Typically, manufacturer warranties cover the replacement of faulty components for a limited time. Failure due to poor installation is typically not warranted by manufacturers. Select a dealer who will do a good job the first time and be around to assist you as needed.