Some semi-serious advice from Aaron Weissblum, co-designer of San Marco and other games:

Make sure you have lots of friends that really like you and are willing to spend many hours testing crappy games.

Play lots of games! When you love a game ask yourself why. When you almost love a game ask yourself what’s missing.

Quit your day job. Recent research indicates that fewer than half of people with day jobs are successful game designers.

http://www.otb-games.com/inventor-of-the-month-aaron-weissblum/