10 Grammar mistakes almost everyone makes

Is there anyone who is so perfect and doesn't make mistake in spoken or written English? 

1. First come, first served
The proper way to write this expressions is "first come, first served," because the people in the scenario will be served in a specific order. The idiom is often mistakenly written as "first come, first serve."

2. Misplaced apostrophes
Adding "apostrophe 's'" to a noun indicates possession. A common area where people misuse apostrophes is with last names.

If your last name is Johnson and you want to invite people to a party, the invitation should read: "The Johnsons invite you to a summer soirée," not "The Johnson's invite you to a summer soirée."

3. i.e. and e.g.
These two abbreviations are often used interchangeably, but their meanings are different. I.e. is Latin for id est, which translates to "that is." Thus, i.e. should be used to clarify something.

It can informally be replaced with "in other words." "He is training for the marathon before work, i.e., he puts in over a dozen miles each morning."

E.g. is short for the Latin "exemplī grātiā," which means "for example."

"I've recently started cooking with local ingredients, e.g., tomatoes and corn."

4. Whet your appetite
This common phrase is often incorrectly written as "wet your appetite." "Whet" means to sharpen. Thus, "whet your appetite" is correct, as it indicates that you're sharpening, or prepping, your appetite to enjoy a meal.

5. Invite/invitation
Formally, "invite" is a verb, and "invitation" is a noun.
However, the English language is constantly evolving, and Merriam-Webster now allows for "invite" to be used as a noun as well.

Thus, both "I haven't responded to her invite yet" and "I haven't responded to her invitation yet" are correct, but the former may annoy some of your more grammar purist friends.

6. Pique your interest
People can often distinguish between the homophones "peek," which means "to look," and "peak," which refers to the top of a mountain or a similar shape.

However, "pique" is used in the phrase "pique your interest," because "pique" means to excite or energize. Thus, if something "piques your interest," that means that it excites you.

7. Brands and 'they'
A brand is a singular entity, thus is takes the pronoun "it." "Kleenex is my favorite brand because they have the softest tissues" is incorrect, since Kleenex is a singular noun.

The sentence should read, "Kleenex is my favorite brand because it has the softest tissues."

8. Piece or peace of mind?
As "peace" and "piece" are homophones, or words with different spellings and meanings that sound the same, be sure to use the correct spelling to be clear on your meaning. "Peace of mind" refers to serenity. To give someone a "piece of your mind" is to harshly express a concern.

9. Then/than
Another classic case of word misuse is between "then" and "than."

"Than" indicates comparison. "I have more time than you do."

"Then" is an adverb used to indicate time. "I had a meeting, and then I went to lunch."

10. Due diligence
To do your due diligence on something is to do a very thorough job. However, "due diligence" is often mistakenly written as "do diligence."

"He exercised due diligence in preparation for the case" is the correct, as it means that the subject went to great lengths to get ready.