• Insert plugs fully so that no part of prongs is exposed when the extension cord is used.
• Disconnecting? – pull the plug rather than the cord.
• Use only three-wire extension cords for appliances with three-prong plugs. Never remove the third (round or U-shaped) prong. It is a safety feature designed to reduce risk of shock & electrocution.
• Noticeable warming of plastic parts is expected when used at maximum rating. However, if cord feels hot or with softening of plastic, this is a warning that the plug wires or connections are failing & cord should be discarded / replaced.
• Never cover any part of an extension cord with newspapers, clothing, rugs, or any objects while the cord is in use. Never place an extension cord where it is likely to be damaged by heavy furniture or foot traffic.
• Don't use staples or nails to attach extension cords to a baseboard or to another surface. This could damage the cord and present a shock or fire hazard.
• Don't overload extension cords by plugging in appliances that draw a total of more watts than the rating of the cord.
• Use special, heavy duty extension cords for high wattage appliances such as air conditioners, portable electric heaters, and freezers.
• When using outdoor tools and appliances, use only extension cords labeled for outdoor use.
(From the U.S. Consumer Product Safety Commission)