Touch is not just a symbolic gesture; it affects the brain in ways that increase trust and rapport. It's an important aspect of our client communications that we probably don't think about enough. But incorporating it into our client meetings is as simple as remembering to shake our client's hand. Even when our client is shackled. And even when he's behind glass (ask the guards for a moment to greet the client before he is settled in the booth; they may actually give it to you). Touch (or a touch substitute) may be important, too, when a client is sharing difficult information. A touch on the arm or the back of the hand, leaning towards the client across the table, or touching fingers to the glass indicates, again: I hear you; I am present with you; I am not afraid of you.
But please! No dead-fish handshakes, no queen's fingertips, and certainly not the Trump grab-and-jerk!
A warm, firm (not crushing!) grip with a "hand hug" on top is a very pleasant handshake.