Use italics for the titles of books, movies, plays, TV shows, magazines, CDs, long musical pieces, works of art, and famous speeches.
Hagrid almost had to drag Harry away from Curses and Countercurses (Bewitch Your Friends and Befuddle Your Enemies with the Latest Revenges: Hair Loss, Jelly-Legs, Tongue-Tying, and Much, Much More) by Professor Vindictus Viridian.
Use italics for foreign words.
Hermione rolled up the sleeves of her gown, flicked her wand, and said, “Wingardium Leviosa!”
Use italics for individual letters or words being discussed.
"Ah," said Arthur, "this is obviously some strange usage of the word safe that I wasn't previously aware of."
Use italics VERY RARELY for emphasis, or you may choose to use italics to show the words someone is thinking (instead of using quotation marks).