"A beard does not constitute a philosopher." 

    - Herodes Atticus

Two of the three people above are philosophers.  The third is not.  I'll tell you who is who, in a bit, if you don't recognize them, but that is not my point.  My point is that you can't judge people by what they look like.  Although the 5 foot 3 inch tall person is unlikely to be a varsity basketball player if you are looking at college students, that same person, if in grade school, could be posting up at center as an absolute dominating monster in the paint!  And, to overplay my analogy, not every six foot six inch tall person LIKES basketball, and you are probably more likely to find a musician than you are a starting power forward.

Don't judge a book by its cover, in other words.

How do you find out about people then?  Ask.  If you can't ask directly, listen to them.

The people above, left to right:

Friedrich Nietzsche - philosopher, mustache, no beard

Grigori Rasputin - non-philosopher (mystic), full-beard

David Hume - philosopher, clean-shaven

Oh, and don't judge Rasputin by those crazy eyes.  I don't think he was crazy.  His mother had him tested.