Braukaiser does the best job explaining lautering efficiency, but he does not offer a way to predict lautering efficiency, which I contend is entirely based on experience with your own equipment. Using Kai's analysis you should be able to better predict your efficiency in the future though. You must be careful though since it's easy to throw off your numbers by measurement error.
That's a very useful chart. I use that chart to predict my pre-boil OG on every batch. It is spot on almost every time and has never been off by more than 0.001. Has been consistent with post boil OGs from 1.034 to 1.086. My methods are probably not relevant in this thread though.