I don't have an exact formula, and probably never will, but the sweet spot for maximizing outgoing link value seems to be to have about 3x as many outgoing links as incoming ones, give or take a few percentage points either way. If you have 10 incoming links, having 30 outgoing will gain you a boost. 20 incoming means 60 outgoing, etc.
Obviously, linking to those linking to you should help. An idea I've been playing with is to also link to blogs that link to blogs linking to me. As long as I have extra links to spread around, seems like a sound strategy.
Problem is many blogs linking to me are in a freefall at the moment, and many have the wrong number of outgoing links to stabilize things at the moment. Might have to ride the fall before the upswing can begin.