Allright. It came up at work today, and I'm totally out of touch. How does one get the best deals on airfare these days? Are things like travelocity.com and expedia.com still the best deals? Is it better to book way in advance or at the last minute?

For examples, let's use San Francisco (or thereabouts) to Providence Rhode Island (or thereabouts). My sister lives in RI and i'd like to go visit her one of these days. If rhode island is too hard, use Detroit or Chicago.