Glenn Leibowitz, a writer and editor by profession, often wonder why some authors didn't take a few moments to check and correct his or her work before proceeding in whatever they want to do with it. Landing a job, closing a deal, inspiring employees and a lot more things are only a couple of examples among the reasons why being able to write well and properly is essential. Leibowitz has listed down eight of the most common writing mistakes that can make one look unprofessional. Take a look at them:

1.  Misspelled words

With every source we have in this world, it's almost as if there is no certain excuse to commit spelling mistakes. There are a lot of ways where we can avoid this mistake, yet it still remains as one of the most common of all. Aside from the automatic spell check, dictionaries and Google are always ready for service.

2.  Inconsistent spelling and punctuation

"Consistency of spelling and punctuation is the mark of a professional writer," Leibowitz says.

3. Wrong usage

For example, the words "compliment" and "complement", "precede" and "proceed" a lot more always get mixed up. The words that sound alike but usually mean different things are the culprits of wrong usage.

4. Confusing contractions with possessive pronouns

Here is a list of the most common mistakes in this department:

It's and its

They're and their

Who's and whose

You're and your

5. Weak qualifiers

 According to Leibowitz, "sort of", "somewhat", "kind of", "rather", "pretty much" are only some of the words and phrases that can weaken a sentence. "Don't say you were a bit confused and sort of tired and a little depressed and somewhat annoyed. Be confused. Be tired. Be depressed. Be annoyed. Don't hedge your prose with little timidities. Good writing is lean and confident," author of On Writing Well William Zinsser says.

6. Sentences that go on and on

"If you find yourself hopelessly mired in a long sentence, it's probably because you're trying to make the sentence do more than it can reasonably -- perhaps express dissimilar thoughts. The quickest way out is to break the long sentence into two short sentences, or even three," Zinsser advises.

7. Walls of text

"Keep your paragraphs short. Writing is visual -- it catches the eye before it has a chance to catch the brain. Short paragraphs put air around what you write and make it look inviting, whereas a long chunk of type can discourage a reader from even starting to read," Zinsser suggests.

8. Lack of focus

"Every successful piece of nonfiction should leave the reader with one provocative thought that he or she didn't have before. Not two thoughts, or five -- just one. So decide what single point you want to leave in the reader's mind," Zinsser says.