I always turn the gas off prior to shutting the engine off. Work requires I travel for extended periods, and then I run the bike with the gas off until the engine dies, and then I drain the carb bowls. I have found from experience that draining the bowls makes a big difference. When I don't drain the bowls and I am gone for more than 3 or 4 weeks the bike is very hard to start. If I drain the bowls the bike starts like I had been riding daily.

Those who would give up essential liberty to purchase a little temporary safety deserve neither liberty nor safety. Benjamin Franklin, US author, diplomat, inventor, physicist, politician, & printer (1706 - 1790)