How can I avoid turning into a pointy-haired boss?

The pointy-haired boss is a manager who doesn't program. So the surest way to avoid becoming him is to stay a programmer. What tempts programmers to become managers are companies with old-fashioned corporate structure, where the only way to advance in salary and prestige is to go into management. So if you want to avoid becoming a PHB, avoid such companies, and work for (or start) startups.