One of the things you most often hear when it comes to choosing any company to do work in your home is to seek a testimonial or referral. Sometimes that is easier said then done. Where do you go to get a testimonial? Will a company provide references? What about online review sites?
When it comes to choosing a heating and cooling contractor many people go with the company that first installed their furnace or air conditioning unit. When you have that past experience with a company that can be very helpful. If the company that did the installation has done a good job you are more likely to seek them out in the future or refer them to your friends and family. If you know someone who has just had a new furnace installed in the last couple of years you may want to get their opinion on whether or not you should contact that HVAC contractor.
If you call any heating or air conditioning company they should be able to point you to testimonials on their website or a consumer review site online with testimonials. Even if you see a negative review online remember that the anonymity behind customer reviews makes them harder to validate and nearly every review site gives companies the ability to work with customers to solve any issues. If you see a review keep in mind that any complaints should be relevant to tangible things such as details about service or installation and not about vague issues.