Throttle operation
The trainer you learned to fly in probably had a carbureted engine. when starting the engine you were told to never push in the throttle unless you were cranking the engine. When doing the annual we learned first-hand why you were told that.
One of the things that we normally do is to lube the throttle, mixture, and carb heat cables. The cable is wrapped in a stainless braid, so we spray the braid and then work the cable a bit so that it gets the cable lubed up. Inside the plane, we just switched to using Tri-Flow and in the engine compartment we continue to use ACF-50.
The throttle cable had been sticking so we worked it in and out a bunch. I then went to lube the part in the engine compartment and noticed a ton of fuel on the floor. We turned the fuel off and lubed the cable in the engine. Even with the fuel off, there was still enough fuel in the system so that a large amount came out of the carb.
Fuel literally was pouring out of the hole in the bottom of the carburetor. If the engine is hot when you move the throttle, you can easily catch on fire.
If you do get a carburetor fire, pull the mixture, push the throttle all the way in, and continue cranking. That will deny the engine of fuel and suck the remaining fuel into the engine where it can safely burn up. It should go out in maybe 15 seconds. If not, get out.