AHRI recommends contacting a NATE-certified technician for assistance in picking the proper equipment for your residence or business. You can find NATE-certified technicians by visiting https://www.natex.org/site/456/Homeowners/Find-a-Contractor-with-NATE-Certified-Technicians.
Regardless of who your technician is, whenever possible, look for AHRI Certified equipment and request your installer provide you with the model's AHRI Certificate of Performance before making purchasing decisions. In addition to giving you confidence that equipment performance claims have been independently measured and verified, you will likely need this certificate, or information from it, if you apply for energy savings related rebates.
You, as well as your technician, can perform free searches of AHRI Certified equipment on the AHRI Directory of Certified Product Performance, ww.ahridirectory.org.
If you are a homeowner, you may find some useful general equipment information and best practices information here: http://www.ahrinet.org/Homeowners.
If you are a contractor or specifier, you may find some helpful information here: http://www.ahrinet.org/Contractors-Specifiers.