The wall outlet should be installed so that the kiln cord hangs downward-not upward-from the wall outlet. Do not place the outlet so close to the floor that the kiln cord bends at a sharp angle. In either case, the plug may not seat properly in the outlet, which will cause the plug to over-heat and corrode.
Make sure the plug is pressed all the way into the outlet. Heavy amperage plugs sometimes work their way out of the wall receptacle due to the weight and movement of the cord. This leads to poor contact between the plug and outlet.
If you smell plastic or hear a faint crackling noise, turn off the kiln and inspect the wall outlet and cord plug.
Remove the plug from the wall every few firings and check for blackened plug prongs and melted or discolored plastic. At these signs of heat damage, replace both the wall outlet and the kiln's electrical cord. Make sure the receptacle feels tight when you press the plug back into the outlet. A loose receptacle indicates worn springs, which will lead to overheating. While the kiln is firing, occasionally touch the cord near the plug, and the wall outlet cover. It is okay if they feel warm, but if they are hot, turn the kiln off. Have an electrician inspect the circuit.
Some people apply a light coating of oxidation inhibitor to the prongs on the kiln plug. This helps insure good contact between the plug and wall outlet. The inhibitor is a paste available at electrical supply stores.