How can one prevent hangovers?

I've got one...don't drink. No,two...don't drink and if you go out somewhere where they're swilling the cocktails, order a "Horse's Neck". It's non-alcoholic and it looks like you're having a drink when everybody else is getting schnockered. You can drink as many as you want and you'll go home knowing where you're going,where your keys are...and no hangover in the morning! It works for me.