Do you remember, from grade school English, how to properly annotate a title?
Titles of books, newspapers, magazines, movies, poems, journals, TV shows, works of art, musical compositions, ships, and airplanes should all be underlined. Or, italicized. They are more or less interchangeable so far as typing goes.
This is because handwriting, of course (does anybody write anything by hand anymore?) doesn’t really allow itself to the option of using italics, so when writing things by hand, underlining is the only real choice. It is also recommended for manuscripts–it makes it clear to see. So, for all intents and purposes, they are the same thing.
Now, quotation marks should be used for titles of articles, essays, short poems, songs, book chapters, and specifics episodes of tv shows.
So, really, it’s easy to remember. The big things get underlines/italics. The smaller pieces get quotation marks. So when you rave about this to all your friends, you’ll want to say, “I read this wonderful post called “MM: Titles” on the Punctuality Rules! blog.”