For starters, don't stalk him As far as casually and safely attempting to run into him, this is my guess:
It's probably too late, but: you could have tried to hang out by the pool at the University of Michigan for the last four years, but Phelps is done with college and supposedly moving back to his hometown in Baltimore, Maryland after completing the Olympics.
If he moves back home: hang around or try to get trained or lessons at the North Baltimore Aquatic Club, where his lifelong coach will be taking the CEO position there, after the Olympics.
It's awful, but: become best friends with a Make-A-Wish kid who really loves Michael Phelps.
It's almost impossible, but: you could become an Olympian yourself. At least you would get invited to the same parties.
Other than that, pray. Pray really hard. But don't stalk.
Go here for some more interesting info. and stats on the Phabulous Phenom Phelps:
http://www.nbcolympics.com/athletes/athlete=2/bio/index.html
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