I am asking for everyones technique on determining when a system has the proper amount of refrigerant.

for example: residential cooling unit found low on refrigerant. What do ya'll use as the determining
factor(s) when charging a system ???

I teach at a local tech school, and this is the semester for teaching the students how to properly charge a system.

weighing & measuring the manufacturers recommended amount of charge, of course
site glass, of course

but, if you have a system that is low, how do you (I have my method ) dtermine when you have the system correctly charged ??