TAROT

OK. This is the first set of words that I’ve accumulated. I’ll be ignoring definitions that don’t seem relevant to the confusion. I’m also going to try to weed out the ones that have come to be accepted, even if I don’t like the way that they look. (To me, you ferment beer, and you foment rebellion, but you can apparently ferment rebellion too. It still looks ugly to me, and ferment doesn’t convey to me the same sense of passionate fervor as foment.)

AUGER/AUGUR

auger (n) device for making a hole
augur (n) one who interprets omens (v) to portend

Before you go ice fishing, you need to get an auger.
This flat tire does not augur well for the rest of our journey.

BREACH/BREECH

breach (n) a hole in a wall made by a gun, a break
breech (n) the back end of a rifle or cannon where you insert the round or shell

He was being sued for breach of contract.
Take these breaching charges, and set them up here and here.
The breech-loading cannon can be fired more quickly than the muzzle-loader.

DEPENDANT/DEPENDENT

dependant (n) someone that you claim on your taxes (i.e. financially support)
dependent (adj.) contingent, reliant (n) as dependant

So, when spelled with an “a,” this word is always a noun, the “e” spelling can go either way (at least, in American). This means that you always write “dependent on/upon.”
The child is dependent on the father for help.
The child is the father’s dependant/dependent.

FLAUNT/FLOUT

flaunt (v) to show off
flout (v) to willfully disregard, mock (usu. law, authority)

A jaywalker flouts the law. If you wanted to flaunt the law you could put on a black robe and dance around waving a copy of the criminal code in the air shouting, “I have a law book!”

LESSER/LESSOR

lesser (n) someone you consider to be beneath you
lessor (n) someone who works at a car dealership

He is unable to hide the contempt that he feels for those he considers his lessers.

LOATH/LOATHE

loath (adj.) reluctant
loathe (v) to hate intensely

I am loath to discuss the matter.
Nazis, I loathe these guys!

PLAIN/PLANE

plain (n) a flat piece of land
plane (n) an alternate frame of existence

I never thought that this would end up on my list, but I read about a man “standing on a snowy plane,” and, even if he was in an alternate reality, he would still be on a plain within the plane.

PORING/POURING

pore (v) to study carefully
pour (v) to dump, to flow

The overused expression here is “poring over musty old tomes.” They’re always old and musty. Once in a while, someone might pore through a law text. Nobody ever pores over Dr. Seuss. To remember this, imagine the wizard has his nose so close to the parchment that he can see the pores in the animal skin.

PRINCIPAL/PRINCIPLE

principal (adj.) primary (n) one in charge of a school
principle (n) a rule or part of a code

The vice principal took the unruly student to detention.
The investment pays five percent of the principal in interest.
It’s the principle of the thing.
While I agree in principle with your request, we need to address some of the details.

RAIN/REIGN/REIN

rain (n) water (or other stuff) that falls from the sky (v) to fall from the sky
reign (n) period of rule (v) to hold power
rein (n) strap for controlling a horse (or other animal) (v) to slow or stop a horse etc.

The expression “free rein” refers to letting your horse go where it wants to. But even better would be to find another way to say unrestrained.
A reign is assumed to be unfettered. To describe it as free is redundant.
It’s a “reign of terror” unless KillBots are falling from the sky, and even then, “Rain of Terror!” would be a cutesy newspaper headline.

TEAM/TEEM

team (n) a co-ordinated group
teem (v) to be full

This is almost exclusively used in one of the following two ways:
The river teemed with fish.
The jungle was teeming with life.
Nothing else ever seems to teem. It’d probably be better to avoid both sentences entirely.

TENANT/TENET

tenant (n) one who pays rent
tenet (n) a guiding principle or belief

An apartment building has tenants, a religion has tenets.

THROE/THROW

throe (n) a violent spasm
throw (n) a toss of an object

The death throes of the creature were unsettling.
She went wild in the throes of ecstasy.

VICIOUS/VISCOUS

vicious (adj.) nasty
viscous (adj.) sticky, flows like honey

A predator is vicious and so are its teeth. If the creature is viscous then it can also be described as a slime, ooze, pudding or jelly.