Use italics for:

  • the titles of books, journals and plays 
  • legislation and legal cases
  • the names of ships and aircraft
  • scientific names of plants and animals
  • foreign words and phrases not commonly used in English.

You can also use italics to add emphasis. 

He took a very long time.

But do it sparingly or it becomes irritating. 

Retain italics that appear in an original quote, but do not set quotes in italics. It is too hard to read in blocks of text. Instead, block indent quotes, or use quote marks.