I've just read this, not tried it yet. But I probably will before too long.
Tune your guitar up. Or, half-up; I've seen it both ways. Either way, enough that there's tension between the neck and the bridge.
Unscrew the neck bolts a quarter turn. This should pull the neck more fully into the the neck socket.
Re-tighten the neck screws. I've seen it written to tune up to standard before re-tightening, but I don't think it would really buy you much more. This is the setup technique that G&L put into their Owner's Manual. Supposedly, you get better contact within the pocket, resulting in more volume and sustain.
In fact, I think I'll set this down and try it on my #2.
I don't know that I hear a difference, but I do know that I tuned it up to Open G (DGDGBD) and after I had done this, several strings were up to a half-step flat. Which implies that something moved. So, maybe it's better. I think I'll have to do something more comparable and scientific with my #1. If any of you guys are gutsy enough to try it, tell me what you think.