Well I finally I'm going to start at a union shop doing commercial and industrial maintenance and service. I'm starting from the bottom as a first year apprentice. But I will be on my way to the big bucks. I really don't want to mess up this new job. Since I'm going to start out doing just pm's, any advice from some of the pros out their their would be great. Like things I should be doing to every unit, so I have a better handle on a unit that is running good. I want to utilize every time that I'm on a unit. That i get some info out of it. To become a better tech. I don't just want to start out by changing out the filter, quick coil/or burner clean, then slap the panels on. then I'm gone with the wind without even knowing if the unit is running good or not. So if any one has a good check list or quick tips on how to get vital info from the unit. That I can gain over time to improve myself over the years, from having my hands on these units. Thanks