I sit, but am very annimated.  I take the mic and walk around after about the 3rd song to greet and BS with the audience.  I'll tell them a joke or 2 and just in general kid around with them.  Then I'll sing a song, usually one with a really nice arrangement and walk around the room.  Then it's back to sitting for awhile, then back on the floor.  I try to pace it so they are never bored.  It works.
Joe
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Songman55 
Joe Ayala 
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PSR S950, PSR S900, Roland RD 700, Yamaha C3 6'Grand, Sennheiser E 935 mic, several recording mics including a Neuman U 87, Bose L1 Compact, Roland VS 2480 24 Track Recorder 
Joe Ayala