Over the past few weeks, I’ve been updating my portfolio. The good news is that I locked in a gain with NVDA by selling 100 of my shares for $212 per share, which I had bought at an average price of $25 about two years ago. The bad news is that I lost money on other investments. To follow Warren Buffett’s rule of investing (“don’t lose money”), you’ll need to determine what not to buy. Honed from my experience, here’s a short list.