1. First-come, first-serveIt should actually be "served." 

Without the d, the phrase above suggests that the first individual who arrives will be the one who serves everyone, which is not the idiom's intent.

2. I could care less

Think about this one for a minute. The way it's written above suggests you possess care which still could be allocated to the situation in question. "I couldn't care less" is correct because it communicates that "I have no more care to give."

3. Irregardless

This is not a word. It's simply "regardless," as in "Regardless of what you think about grammar, you'll look silly if you use it incorrectly."

4. "I" as the last word in a sentence.

This mistake is remarkably common, yet a correct example would be "Karlee talked with Brandon and me." The trick to getting this one straight is to take the other person's name out of the sentence and see if your personal pronoun choice still sounds right. "Karlee talked with I" is awkward and incorrect.

5. "Me" as the first word in a sentence.

I hear people saying things such as "Me and Brandon met at Starbucks this morning" all the time, even though it's always wrong. "Brandon and I met at Starbucks this morning" is correct.

6. Shoe-in

"Shoo-in" is what you really want to write when you're trying to say that someone is a sure winner. It's because when you "shoo" something you're urging it in a certain direction.

7. Emigrated to

"Emigrate" and "from" always go together, as do "immigrate" and "to." To emigrate is to come from somewhere, and to immigrate is to go to somewhere. "Colin emigrated from Ireland to the United States" means the same as "Colin immigrated to the United States from Ireland."

8. Overuse of apostrophes

These little guys are ubiquitously misused. Apostrophes indicate one of two things: possession or letters missing, as in "Sara's iPad" and "it's" for "it is" (second i missing). They don't belong on plurals. "FAQs," for example, should not have an apostrophe. Also, people often make a mistake with their own last name. If you want to refer to your family but don't want to list everyone's first name write "The Johnsons" not "The Johnson's." Another big one: Decades should not have apostrophes. For example, "1980s" is correct but "1980's" is not.

9. Prostrate cancer

This one is a simple spelling mistake resulting from an extra r. "Prostrate" actually means to lie face down. The "prostate" gland is a part of the male reproductive anatomy.

10. Slight of hand

A "slight" is an insult, whereas "sleight" indicates dexterity or cunning. It's why "sleight of hand" is commonly used in the world of magic and illusion.

11. Honed in

Just know that to "home in" on something means to move toward a goal, such as "The missile homed in on its target." To "hone" is to sharpen.

12. Baited breath

When I think about bait, worms and lures come to mind. The first word should actually be "bated," which stems from the verb "abate," meaning to stop or lessen. So, if you're trying to say that someone is holding his breath, you can see that "bated breath" makes the most sense.

13. Piece of mind

If you want to share what you're thinking with someone, this could work if you add "my" before "mind." But if you're trying to indicate tranquility, then spell it "peace."

14. Wet your appetite

"Whet" means to sharpen or stimulate. As such, the latter spelling is more appropriate.

15. Make due

"Due" means "owed," and that's not the intent with this idiom. "Make do" is the proper way to say that you're going to get along with what you have.

16. Do diligence

"Due diligence" is the proper business and legal term. It means you will investigate an individual or company before signing a contract.

17. Peaked my interest

To pique means to arouse, so the correct phrase is "piqued my interest," meaning that my interest was stimulated. While the incorrect way it's written in the heading may suggest that someone's interest was taken to a high level, it's still wrong.

18. Must of, should of, would of, and could of

All those ofs should be "have." The proper versions were corrupted by contractions such as "must've."

19. Per say or persay

Both are incorrect because the Latin phrase which means "in itself" or "intrinsically" is spelled "per se." The best communicators speak and write clearly and concisely and probably avoid phrases like this one anyway.

20. All the sudden

Whether you say "all of a sudden" or "all of the sudden," the preposition "of" must be involved either way. But if you're really trying to say "suddenly," just do.

21. The first-year anniversary

The use of the word "year" is redundant. "The first anniversary" or "the 50th anniversary" suffice.