A microscope check would be the best option to see if most trichomes are still clear ( not yet time to harvest ), milky ( good to harvest for most people ) , milky/amber ( it's time to harvest ) and all amber ( high time to harvest ).
I cant be more precise
You can always cut a little early, cut most when you feel it's ready, and save a little to cut after. Make sure you keep them separate or labeled during dry/cure and you can compare, see which high you prefer.