Electric Stove: (uses electric coil that glows to cook)
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1. Find the breaker panel in your basement / garage/ closet/ somewhere. Your house has one or you have not electricity. Find this somewhere:
http://haedwardsinc.files.wordpress.com/2011/01/breaker0.jpg
2. Find the switch labeled Stove / Range / Oven / Kitchen Appliances and switch it off. You will know it is off because all the other switches will be on and it will look out of place when it is off. I can't tell you off is right or left because it depends on which side of the panel the switch is on. You will have to push the switch sideways hard.
In this picture of the breaker box, all the breakers are currently on:
http://content.angieslist.com/cms/images/topic_centers/electrical/breaker_box3.jpg
So if you were to flip any switch to the other side it will be in the off position.
Gas Stove (uses fire to cook)
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1. Find the gas line in your house, or the one going to your stove if you can. Look for something like this if you can.
http://farm5.static.flickr.com/4045/4438543138_353f31f510.jpg
In that picture the gas line is off because the handle is pointing away from the direction of the gas line. Notice how it makes a perpendicular angle with the line.
Here, this picture explains it well:
http://0.tqn.com/d/homerepair/1/0/s/A/-/-/gas_valve_position.jpg
If you can't find a valve close to the stove then you may have to turn off all the gas to the house. There must be a way to turn off gas to the house, every house has this because it is a safety guideline. You could not buy / rent your house if you could not turn off the gas.
2. Find the valve and turn it off.