1. Ask for references from friends, neighbors and or co-workers. Do not buy from door to door solicitors, especially after a big storm has just blown through.
2. Lennox, Carrier, Trane/American Standard have Dealer locator's on their web sites. Stick with the big three major brands. Their technical/engineering support and parts availability will pay off in the long run. Angie’s List and Service Magic are other sources.
3. Ask to see the Contractor’s license and insurance, requirements vary by state. If you live in a $750,000 house and the contractor only carries $500,000 worth of liability insurance, he is not the contractor for you. Some states you can look up complaints and current license info on line.
4. Ask for and call recent references. Be sure to ask enough questions to make sure they are real. What type equipment did you have installed, did they show up on time, did they clean up when job was completed, stick to original estimated cost, happy with service, anything wish they had done differently, anything not happy with or don’t like, etc.? You can’t compare prices, no two jobs or houses are the same.
5. Give the estimator / salesman time to do his job. He needs to measure your home, look in your attic and or basement. He also needs to ask you a series of questions about what you may want in a new system. Do you have someone in the home with allergies? Are you a light sleeper, and want a quiet system? Do you have fine antiques and want a humidifier? Are you moving soon, and want the cheapest thing you can your hands on? Do you have some rooms that are hot and others that are cold? Do you like to eat dinner in your recliner, and the vent is pointed right on your plate of food, cooling it off every night, you hate that? Guess what? The contractor’s not a mind reader. We can fix all these problems, but you have to tell us about them first. Allow two to three hours. Yes, I know if you get three bids that’s six to nine hours of your time and you have to hear the salesman crack the same joke about your Peyton Manning life size poster again and again.
6. Don’t fall for you have to buy tonight “discount”. Take your time. There is some reason they don’t want you to shop around. What are they afraid of?
7. Don’t fall for a huge discount. Dealers who advertise thousands off a system, they have just marked it up to mark it down. Same with a free furnace or other product giveaway. It is in the price somewhere. There are utility rebates and government tax credits on some systems. But even on manufactures rebates the dealers has to buy into those, so somehow some way the dealer has to figure that cost back into their price. Nothings free, you know that!
8. Get it in witting. I don’t mean on the back of a business card. Any and everything that is going to be done, list of what equipment you are getting, including warranties need to be written in a detailed proposal.
9. Ask lots and lots of questions. It is the contractor’s job to educate you. If that takes four hours and six, twelve phone calls or emails for you to feel comfortable then that’s what it takes. It’s your money and it’s a lot of money, it’s ok. Call, email, ask away, ask until you fully understand and feel good about what you are buying and getting!
10. When it comes time to compare your bids. Compare apples to apples. Same SEER rating and size, make sure they both include that extra duct run you wanted, or same type of upgraded thermostat or filter system. I recently bid against a contractor and when following up with the customer he told me I was a $1,000 higher another company. I asked if the other company had included the thermostat his wife liked so much or the Honeywell filter he wanted. He told me he wasn’t sure, he would call me back. About 30 minutes later he called me back. He said, “You got the job”, those *&#+%@ weren’t even going to replace my 20 year old furnace, can you believe that? I can’t imagine what that bid looked like, that this gentleman didn’t even have a clue as to what equipment was to be replaced or even what thermostat or filter he would be getting.
11. If the sales person suggests you skip the city permit or building inspector process beware. Or if they ask you to go pull the permit, my guess they have been banned in this city. Hugh red flag!
12. You need to know who is going to be installing your equipment. It probably will not be the clean cut, nicely dressed, well spoken, polite young man who sold you the system. Ask! Do you use sub contractors to install my equipment? Are they insured? Who will be supervising the crew? What type of background checks do you do on your installers? You do not want ex-convicts and drug attics around your family and valuables.
13. Any reputable company accepts checks, credit cards and offers financing options. They may offer a cash discount if you pay with a check or cashier’s check. If the company is asking for green money only, I am thinking something’s not on the up and up (IRS tax avoidance scam). Your payment check should be made out to the company not an individual employee’s name. Also, there is no reason for a big down payment. Your contractor should have accounts at all the supply houses to buy the necessary parts and equipment without needing you to pay for supplies upfront. Anything more than a $100 refundable deposit to show you are serious and hold your spot on the install board worries me about the financial reputation of this contractor. Are they on a cash only basis with their suppliers? 
14. Lastly, your system should come with a 100% money back guarantee. If anytime within one year you are not completely satisfied they will come take the system out and refund 100% of your money. If there is anything you are unhappy with let the contractor know, most will bend over backwards to try to resolve any issues and make you happy.
85% of the contractors out there are good decent hard working people, 5% are stupid, and 5% are lazy. I hope I have done a good job of warning you about the other 5% that I wish it were legal for me to run over with my car.
Pictures courtsey of Google Images.