I received an email from an intern asking for SEO advice specific to backlinking. Obviously, I didn't give away the farm (I charge for this stuff, after all), but I did have one piece of advice anyone trying to figure out why a competitor is doing better than you are in search.
The best thing about SEO is that when you see a site doing it well, there aren't any secrets. Look at the pages, and look at the source code. See what they're doing, and see what you could be doing better.
That's it. You want to know what someone's doing? Look. In some cases, you may have to dig deeper (Yahoo! Site Explorer, Google Webmaster Tools), but nothing on the Web is a mystery. If you see someone doing something well, you don't have to ask how they're doing it, just use your eyes.