Great breakdown of the cinematography basics behind Breaking Bad over at The A.V. Club, as dissected by Scott Kaufman (expect spoilers through Season 5 part 1 in the full article):
Breaking Bad relies more heavily than most shows on what are called “tight singles,” or shots in which a single character occupies the majority of the frame in shallow focus. The background is usually out of focus because it’s unimportant—if you’re watching a show set in a coffee shop, you don’t need the background in focus to remember where the characters are—but in Breaking Bad, the relationship between the planes of focus (foreground, midground, background) typically matters.