"Also, avoid all awkward or affected alliteration."
— William Safire, How Not to Write
Alliteration is the repetition of the first sound of a word. Some authors do this to make the phrase memorable or cute. While that may work, it does not necessarily make for good writing. Many readers find its a bit annoying, even though it works quite well in spoken language. You want the reader to continue reading, not throw the book across the room.
So remember: avoid alliteration always!