You should first ask yourself what you really enjoy. I happen to enjoy reliability, scaling up systems, etc. So I go after those kinds of projects. The things y

You should first ask yourself what you really enjoy. I happen to enjoy reliability, scaling up systems, etc. So I go after those kinds of projects. The things you really enjoy, you'll bring infectious enthusiasm to, and that's the best kung fu you can possess (well, that and learning your craft very well). I would as a general rule avoid anything involving being perceived as QA (stigma), or extremely speculative projects (Google+) -- because you only get one life, and keeping risk of ruin down is good. But, you may disagree and decide to go for risky things. The ROI on those is hard to calculate anything like precisely so it's more a matter of taste than math.