Plague Words
People learn by imitating what they see. That’s how children learn to speak; it’s also how most people learn to write and otherwise express themselves. You might call this “education by contagion”. While it is a workable system, it does have some drawbacks.
One of these drawbacks is when instead of ‘catching’ a good habit, you begin imitating something which is actually wrong. Another person sees you, and does the same. Soon, an incorrect meme spreads and brings down the level of clarity. Contagion becomes a plague.
Some common plague words:
And/or: Outside of the legal world, most of the time this construction is used, it is neither necessary nor logical. Try using one word or the other.
Irregardless: No one word will get you in trouble with the boss faster than this one.
Of: Don’t write would of, should of, could of when you mean would have, should have, could have.
Many similar linguistic pitfalls are covered under Plague Words and Phrases. It makes for a good checklist.