Portable Electric Generator

The Electrical Safety Foundation International offers the following tips:

Do not connect generators directly to household wiring without an appropriate transfer switch installed. Power from generators connected directly to household wiring can backfeed along power lines and electrocute anyone coming in contact with them, including lineworkers making repairs.
Make sure your generator is properly grounded.
Keep the generator dry.
Make sure extension cords used with generators are rated for the load, and are free of cuts, worn insulation, and have three-pronged plugs.
Do not overload the generator. A portable generator should be used only when necessary, and only to power essential equipment or appliances.
Never operate the generator in enclosed or partially enclosed spaces. Use carbon monoxide detectors in nearby enclosed spaces to monitor levels. Generators can produce high levels of carbon monoxide very quickly, which can be deadly.
Use a ground fault circuit interrupter (GFCI) to help prevent electrocutions and electrical shock injuries.
Make sure fuel for the generator is stored safely, away from living areas, in properly labeled containers, and away from fuel-burning appliances. Before re-fueling, always turn the generator off and let it cool down.
Turn off all appliances powered by the generator before shutting down the generator.
Keep children away from portable generators at all times.