Make sure they’re curly and point downward
The apostrophe has two functions we all remember from sixth-grade English class.
An apostrophe indicates the possessive case (Jessica’s bagel).
In contractions, an apostrophe takes the place of letters or numbers that have been removed (is not becomes isn’t, Patent No. 5,269,211 becomes ’211).
Apostrophes always point downward. If the smart-quote conversion feature of your writing system is on (see straight and curly quotes), then type an apostrophe with the same key you use to type a straight single quote '. Your word processor will convert this character to a curly apostrophe ’. Or you can type an apostrophe directly, using the same key as a closing single quote.