monkeydelarge: Be patient and wait. But when you see a game you want that is 80% off or cheaper, then go for it because there might not be such a good deal again later down the road.
I think that's bad advice, unless this falls under the "game you're planning to play soon". It's a slippery slope. I think it's fine if you buy several such games at the year end sale and just play the bunch later, but if you follow sales year round, you soon end up with "this game is 80% off and sounds rather interesting; probably won't play it any time soon, but it's a good addition to my collection". Then you start buying bundles left and right because a game in them caught your eye and it was all "such good value", and soon enough you have a huge backlog.
Edit: I see you edited the message. If you're talking about the Steam sale, then yes, it's good advice to buy stuff only at daily or 12 hour deals and wait for the rest until the end.