[Syonyk]

If you have a beard, thoughtfully stroking it works too.

I joke it's the Windows 98 hourglass cursor of personal interactions - they can't tell if you're thinking, or have just locked up with no hope of continuing.

Pauses and silence are OK, to a point.

Absolutely. And you will, in almost every case, come across as more intelligent if you're silent while thinking, than if you try to fill space with content-free filler. It can't go on forever, but 20 seconds of silence is far better (and far more useful to put a response together) than 20 seconds of "lips in neutral" noise.