Rule 1
Use the apostrophe with contractions. The apostrophe is always placed at the spot where the letter(s) has been removed.

Examples:
don't, isn't
You're right.
She's a great teacher.

Rule 3
Use the apostrophe where the noun that should follow is implied.

Example:
This was his father's, not his, jacket.

Apostrophe rules part 1

Rule 2
Use the apostrophe to show possession. Place the apostrophe before the s to show singular possession.

Examples:
one boy's hat
one woman's hat
one actress's hat
one child's hat
Ms. Chang's house

NOTE: Although names ending in s or an s sound are not required to have the second s added in possessive form, it is preferred.

Examples:
Mr. Jones's golf clubs
Texas's weather
Ms. Straus's daughter
Jose Sanchez's artwork
Dr. Hastings's appointment (name is Hastings)
Mrs. Lees's books (name is Lees)