I'd depart just slightly from bigted's method, though the principles are the same. First, I'd begin by draining the fuel tank, and if it has an air purge system, I'd drain the carburetor by using that. Then after the multiple starter pulls with the spark plug out, I'd put a couple of spoonfuls of mixed 2 stroke fuel into the cylinder or the carburetor air intake, rather than putting straight petrol in. The reason for this difference is that I've seen people use straight petrol either repeatedly or in excessive quantity, and the result has been dry, squeaky, partly seized piston rings when pulling the engine over. Standard 25:1 or 50:1 mix will readily pick up both petrol and oil from the crankcase, and will do the clearing job very well.
After the fuel-clearing exercise, before putting fuel in the tank and trying to start it, I'd test the spark carefully. Chances are you will at a minimum have to wash and then scrape the spark plug to get it firing properly. It's possible though that the plug will have to be replaced.
