Potency, like Terps, are genetics. You make it as cozy for the plant as she likes it most, she will reward you.
You can be a grow guru and still not be able to turn shit into gold... the breeders give you potency level indications. GSC is in general given as 18% THC content... we even reached on one batch 18.6%. So there is also a little space upwards. Also to mention, the average potency test result in SA is 12%... what brings most people back to reality rather fast. Growing weed is one thing.. growing really potent weed needs perfection in every way.
My preferred weed.. Gelato.. gets set by the Breeder at 26%.. I haven't reached that even close. 19isch I get, but 26 i am very far out.. but I creep slowly up in potency too.. learning the strain takes time.
Next factor of potency is how you dry, cure and store it. Wrong way and you reduce potency.
So to make it short, if you keep all parameters from Germination, Veg, Flower, Harvest, Dry procedure, Curing procedure and Storage in the green areas.. you will get rewarded with the potency the plants genetics have to offer.
Anything else.. Veg to dry, flower to wet, Temps out of range (18-25 i see as sweet spot range), dry climate off, cure humidity to low or to high, ... any pest hindering the plants development, any feeding lockout or deficiency, light strength, leaf sugar content.. every factor will reduce a bit potency from the max to reach. You want max potency weed, you have to be perfect yourself.