Which is more appropriate Shaking hands or hugging an old acquaintance in a business meeting?

Between men in a business meeting, a firm handshake, perhaps accompanied by a loose hold on their lower arm with your left hand, is the most that would be appropriate, unless you both come from a more demonstrative culture.

Even between women, in a business meeting hugs would not be correct, although sometimes you do see "huggy" people moving in for the clinch. A gentle handshake would be much better.

Offer a handshake. Better to be overly formal than overly informal.

I am a hugger, so I would give a quick hug.

whatever you want to do