You can perform the simpler tasks such as checking for restrictions in the airflow that are typically caused by dirty air filters. Additionally, if you have a weak airflow, there may be a problem with the blower or the ducts. In that case, you should hire an HVAC contractor or technician to correct those issues.

Ask a dozen HVAC industry experts what the key to fewer expensive repairs and longer A/C system life is and they will all answer that, without a doubt, it is regularly scheduled cleaning and preventative maintenance. HVAC contractors and technicians have the experience, expertise, and knowledge of the many aspects and elements of heating, ventilation, and air conditioning operations. 

If you're installing central air, you need to consider three things: the quality of the equipment that you buy, the output and efficiency of that equipment, and the experience of the contractor installing it. 

A heat pump is essentially an air conditioner that can both heat and cool a house. A simple explanation of how this works is that a heat pump can extract heat found in the air outside your home and transfer that heat into your house instead.