Note: Rewriting is sometimes the solution for an awkward possessive.

Awkward: A friend of mine's cap.

Better: A friend's cap (or the cap of a friend of mine).

To show possession in the case of singular nouns, add 's, and for plural words that end in s, add only an apostrophe. Don't forget to put 's with plural words not ending in s.

Example

Singular: nurse's uniform

Plural: nurses' uniforms (plural word ending in s)

Plural: children's uniforms (plural word not ending in s)

Use of Comma - Use commas to separate three or more items in a list. Though journalists most of the times omit the final comma before the word "and", but retaining the final comma avoids confusion.

Example

Poor: In this website, you can read articles about how to do business online, the woman who daily eats 45 eggs and Tom Cruise.

Better: In this website, you can read articles about how to do business online, the woman who daily eats 45 eggs, and Tom Cruise.

Use a comma to separate two independent clauses joined by coordinating conjunctions.

Example

Wrong: I am not good in writing but I love writing.

Wrong: I am not good in writing, but, I love writing.

Right: I am not good in writing, but I love writing.

Note: If the clauses are long and already contain commas, separate them with a semicolon rather than a comma.

Wrong: If a man begins with certainties, he shall end in doubts, but if he will be content to begin with doubts, he shall end in certainties. - Francis Bacon

Right: If a man begins with certainties, he shall end in doubts; but if he will be content to begin with doubts, he shall end in certainties. - Francis Bacon

Run-on sentences - Where Run-on sentences are concerned (in case you don't know what it is, a run-on occurs when two independent clauses are not separated by punctuation or conjunction), add a period, or a semi colon, or a comma in places of separation.

Example

Wrong: A good student can score full marks in Mathematics it's his analytical ability that will help him achieve that.

Right: A good student can score full marks in Mathematics. It's his analytical ability that will help him achieve that.

Use of Quotation Marks - Use quotation marks to indicate direct quotation.

Example

"That guy knows me," Mr. Wong said, "very well."

Note: Never use it for indirect quotation (a restatement of someone’s words).

According to Mr. Wong, that guy knows him very well.

Use single quotation marks to indicate a quote within a quote.

Example

Wrong: Richard wrote, "When Berkeley said, "esse est percipii", he meant that the existence of a thing consists in its being perceived."

Right: Richard wrote, "When Berkeley said, 'esse est percipii,' he meant that the existence of a thing consists in its being perceived."

Note: Always put the comma and final period inside the quotation marks, and put other punctuation marks outside unless they are part of the thing being quoted.

There are many other frequently used punctuation errors, but the above-discussed ones are those I have mostly encountered in several writings. Before putting punctuation marks in your sentences, always ask yourself what meaning you want to convey to the readers. Accordingly, put the marks. In case the sentence becomes difficult to punctuate, consider rewriting it, because when a sentence is well written, it almost punctuates itself.