How do you decide what games to buy?

Amazon's Game Room has an interesting post exploring all the different factors that go into making a game purchase, outside of game play that is. Items for consideration include genre format, review scores, price,
replay value, ESRB rating (for those with offspring), and loyalty (aka nostalgia or the fondness factor) to name a few. Click over to see the full description of all 12, and for the sake of discussion, which non-game play determinants influence your purchasing power? Be honest.