I personally don't have any rules and just look at it organically. I bear in mind that concentration is what gives you dramatic outperformance, but try to keep risks in mind. I've had upwards of 40-50% in one position, and currently have 2-3 > 20% positions. That being said, I'll probably have a portfolio similar to Gio's at some point (or at least a large portion of my port similar to Gio's), once my ideas play out (e.g., AIG, BAC, etc.).