Summarize:

Lightning often strikes the tallest object in the area, so avoid open fields or any hilltops. Look for a low-lying area like a valley or ravine, preferably obscured from the rain. Take refuge here until the storm passes. Crouch down with your heels touching and your head between your knees: this will make you a smaller target. Do not lie down flat, and minimize your contact with the ground. Lightning can be fatal up to one hundred feet away from the initial strike. Check weather forecasts early in the day, and avoid going to a swimming pool, river, lake, or beach on rainy days. If you find yourself in open water during a thunderstorm, return to land immediately. If you are in a boat and cannot return to safety, drop anchor and crouch as low as possible.  Do not return to the body of water until thirty minutes after the last lightning strike. Any earlier, and the storm may not be over.  Indoor swimming is equally unsafe. Avoid all large bodies of water during a storm. Taller objects are more likely to be struck by lightning. Wherever you are, don't become the highest object anywhere. Avoid standing under trees in a lightning storm, and stay away from tall objects like light posts.  If you're in a forest, stay near a lower stand of trees.  Umbrellas can increase your risk of getting hit if it is the tallest object in the area. Metal conducts electricity, and you are much more likely to get hit. If you are carrying large metal objects, let them go. Small metal objects, like piercings or electronic devices, do not carry a large risk and are safe to hold.  If you are riding a bicycle, drop the bike and crouch to the ground. Most bikes are made of metal and are excellent lightning conductors.  Rubber shoes or other rubber objects will not actually protect you from metal's conducting properties.
Stay away from open fields or hilltops. Avoid swimming or watersports on rainy days. Don't stand near trees or tall isolated objects. Avoid metal objects, like fences or exposed pipes.