Before hitting he starter button use the kick tart or spanner on the crank to turn engine over a few times before switching the ignition on.
Once it starts just don't rev it immediately, let it idle initially.
This is pointless advice, it does nothing.
It ensures that little force is used when scrapping the rust off then barrels to save the piston rings snapping.
Simon. As an engineer for many years it is to a barrel scraping excuse, it is an exercise in scraping the rust off the barrel gently.