VIDEO HERE (9:11 minutes)
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It's all common sense stuff, but I think #1 is the most important. The only time I've killed my generator with the switch is when I know I'm going to be restarting it within the next hour or so, but 99% of the time I just cut the fuel off and let it starve.
It's paid off, though - I've had that generator for over 8 years and never had to have the carb rebuilt or replaced and it always starts on the first pull or two. It also helps that I fire that sucker up and use it at least once a week during the summer (I have no power in my shed) and once every couple weeks during the winter.