Use vs Utilize

Don't use the word "utilize." It's just a pretentious way to say "use." There isn't anything really wrong with the word utilize, but it makes your writing clumsy and less clear.
In Britain, "utilize" is spelled with as "s." Don't use "utilise" either.

Stationary vs Stationery

Stationary is an adjective meaning motionless. Don't try to change a tire unless the car is stationary.
Stationery is paper, especially fancy paper or paper printed with a company letterhead. Use nice stationery if you write your mom a letter.

Principle and Principal

A principle is a belief or a point of honor. I always take my bottles to the recycling depot, not for the refund but as a matter of principle.
"Principal" means "first" or "top-ranked." The principal of a school is the top-ranked person there. I'm scared of mice, but my principal fear is snakes.

Avoid Confusion with Pronouns

Every pronoun is a potential problem. Each time you say "he, " "she," or "it," asks yourself if there is any way the pronoun can be misunderstood. It is not always obvious where misunderstandings can occur, because you, the writer, always know what you mean. You, however, may be the only one.

Consider this example:

Andy said he ran into Bob and Carl the other day. He said he stepped on his toe, and he was really mad about it. He said he was sorry.

Who did what? Your guess is as good as mine.

Affect vs Effect

Affect is a verb. Things affect other things.

Effect is a noun. Things have effects.

The weather didn't affect me. It had no effect on me.

proceeding away from clarity

A bizarre thing happens when the average citizen is asked to fill out a police report. Suddenly clear communication disappears as the civilian decides he must sound official.

"I was proceeding down fourth street..."

How were you proceeding? Driving? Walking? Riding a stolen shopping cart while sound asleep?

Avoid words like "proceeding," words which hide their meaning. There is nothing wrong with saying, "I was walking" or "I was driving." People should know what you actually mean.

"She" vs "Her"

Wrong - "Her and her friend are going to the store."

Right - "She and her friend are going to the store."

To get it right, leave out her friend. You would say "She is going to the store," not "Her is going to the store." She is going to the store; She and her friend are going to the store.