This assumes of course that your friend has a smartphone and is curious about Bitcoin. Just say you wanna buy their lunch..... and show them how to pay the bill with Bitcoin.
 

• Go to lunch; They drive, YOU buy
• Go to the app store to download and install the Mycelium wallet (or your fave)
• Send your friend enough bitcoin to pay for lunch
• Show them how to pay the bill with their phone
• Thank them for buying your lunch

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• When you get back home, show them how to do a backup, buy online, get more Bitcoin, work for Bitcoin, get a coinwidget or changetip address for their social pages (ie: kenCode.tip.me), etc.
• Send your friend another couple bucks for the gas money
• Next time, THEY buy for someone, and so on

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If we all start buying each other lunch, just think how many more businesses will come on board with Bitcoin!