Earlier this week, J.D. wrote about what he calls the biggest truth in personal finance: You can't get rich through frugality alone. As Liz at Frugalwoods says, “You can't frugalize income you don't earn.” Income is one-half the fundamental personal-finance equation, and it's probably the most important half. J.D. advocates a three-pronged attack for boosting income: becoming better educated, becoming a more valuable worker, and learning to negotiate salary.