How do I take a Screen Shot?

How do I take a screen shot? do I need any special programs? Thanks
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I'm so constipated I've become a prune juice conesuir (sp)

'peter north is fucken awesome, hes got a big rod and blows gallons of semen on fresh 18 year old faces
-lateralis

'It isn't pollution that's harming the environment. It's the impurities in our air and water that are doing it.'
-Dubya.

'I would never do crack... I would never do a drug named after a part of my own ass, okay?'
Denis Leary.

'You're not drunk if you can lie on the floor without holding on.'

'Not all chemicals are bad. Without chemicals such as hydrogen and oxygen, for example, there would be no way to make water, a vital ingredient in beer.'

'Cocaine is God's way of saying your're making too much money.'
Robin Williams.

'I don't like people who take drugs... Customs men for example.'