The basic rule is this:
- Any work long enough to be published alone is put in italics,
- Shorter works or parts of longer works are enclosed in (double) quotation marks.
Thus titles of books, novels, plays, long poems, periodicals and so on (operas, ballets, named symphonies, newspapers, sculptures, paintings, television programs, ships, planes, and spacecraft) are in italics, whereas any item that appears within a larger work--single poems, articles, short stories, chapters, titles of songs and so on--are enclosed in quotation marks.
If you're typing your essay and can't italicize words, underline them instead.