An interesting question, trickier than it seems at first glance.  For now, 
not being Baron, I wouldn't assume that someone I'd seen at three events was 
necessarily new; on the other hand, if I've never seen them in garb, I 
wouldn't assume that they're necessarily members at all yet, either.  What is 
the nature of this event and of the past two?  If they've all been semi-open 
events like Falling Leaves or May Day, I would probably approach the person 
in an open and friendly manner as an evidently interested potential member; 
I'd talk to them about what their interests are, and try to link them up with 
some loaner garb and invite them to "come inside."
<p>
On the other hand, if I've been seeing them at more closed events where they 
evidently paid a site fee and otherwise consciously chose to come in, I'd be 
less likely to come straight over.  I'd probably ask around a little first, 
see if anyone knows who this person is, whether anyone else has ever seen 
them in garb (maybe I've only seen them coming to or leaving the event), 
whether anyone else had already talked to them in the manner suggested above. 
 I'd likely still approach them and engage them in talk, but just what tack 
I'd take would depend on what I'd learned from the asking-around stage.
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I would likely do things a little differently as Baron.  If they seemed shy 
and genuinely unaware, I'd worry lest having The Baron Of Carolingia approach 
them might be intimidating (gentle and lovable though I am); I'd probably ask 
a known responsible and discreet friend (member of entourage?) to go and try 
my first approach.  On the other hand, the more it seemed that they had 
already had some exposure to our mores but just didn't care, the more likely 
I'd be to approach them in person - still open and friendly, but letting them 
know that collective appearance really does matter to us.
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I can't give a clearer answer, it would depend a lot on the situation.
