[quote=@Meta]
<Snipped quote by Codify>

What about just the things that work on almost everyone? Or the most useful things?
[/quote]

Hmm. That really depends on what you're dealing with. Mammal, lizard, etcetera... There's rarely things that work on "almost everyone." And what's most useful depends on what you're dealing with. Sorry if this seems obtuse, but it's why having a specific goal in mind is easier than trying to learn "everything."