A. Here’s the problem:
Correct formation of possessive nouns—‘s for single possessive, s’ for plural possessive—stays in the no excuses, no mercy category. But two other possessive rules deserve quick mention here because they pop up like unwanted weeds in your writing.
B. What to do:
1. Its is a possessive pronoun, referring to some quality or property belonging to it; it’s is a contraction meaning “it is.” Possessive personal pronouns don’t take apostrophes; contractions do.
2. A pronoun before a gerund is in the possessive case.
C. Example: When Mr. Bingley spoke of his four to five thousand pounds a year, Mrs. Bennet thought of him marrying one of her daughters.
Corrected Version: When Mr. Bingley spoke of his four to five thousand pounds a year, Mrs. Bennet thought of his marrying one of her daughters.
D. Now you try—write corrected versions of the following sentences.
1. Mother objected to us driving on the icy roads.
2. She understands how marriage was dictated by her setting and its idea that the union between a man and a woman existed primarily to better one’s status in life.
E. For more information or additional practice, check the following sources:
Strunk & White, p. 12 or http://www.bartleby.com/141/ http://grammar.ccc.commnet.edu/grammar/gerunds.htm#possessive
