wow... ok... I'll bite.
1. Intent.
what are you looking for to add to your female? need to tighten nodes? wanna stretch an indica leaning hybrid? looking to quicken up a late bloomer with a quick to flower strain? looking for a specific aroma or flavor? what the hell are you doing?
this is a subjective portion that you must decide... what traits do you want in your intended cross?
2. Traits.
what I look at is:
Resin production... the quickness, the amount and location.
Aroma... many good males have a distinct smell.
Quickness to flower... subjective trait based off my intent.
Internode spacing... subjective based off intent, but generally shorter is better.
Structure... subjective. the plants general structure, is it leaning to sativa or indica?
Resistance to hermaphrodism - see #3
Vigor and fitness - see #3
3. Stress testing.
methods used include:
heat and cold, overwatering, underwatering, rootbinding, rootball pruning, topping or supercropping in flower.
In stress testing you're looking to weed out males that are likely to produce intersex traits or poor vigor... the basic idea is to present the worst possible conditions and look for hairs that pop, how easily, how quickly and how many. Then consider the plants quickness to recover throughout those tests to gauge its general vigor.
A mouse is not an "elephant" solely because it has characteristics that are common to known elephants: a tail, gray skin, larger ears and four legs... there is also an artistic aspect to the science...