Have a high school diploma or a GED. You'll need to have good basic math skills and be able to read and use measurements. You'll need to be able to work accurately to precise specifications.
Consider enrolling in a local technical school. The training you can get at a tech school will prepare you to work with the equipment involved in HVAC work and teach you electrical codes as well. Safety and standards training will be included. Many tech schools offer externships that will provide you with future contacts and references for your resume when you're ready to start your career.
Get HVAC training online. There are courses available for certification and training as a heating and air conditioning mechanic. You'll get training in installing, servicing and repairing HVAC systems. Both commercial and residential courses are offered. You can also register to take the EPA certification test online.
Check with the local HVAC service and supply companies in your area. Some offer apprenticeship programs for high school graduates. You can get on-the-job training. You'll also learn the difference between natural and LP gas lines, low and high voltage electricity and how to read air-flow measurements.
Advance in your training by attending seminars provided by manufacturers of HVAC systems. Training there will include Freon handling. You'll also get a wide range of exposure to all kinds of systems. Oil heating systems, electric heat and air systems and solid fuel systems will be covered.