I don't usually say anything unless I've given it a couple seconds to consider whether it's worth saying. People tend not to like standing there with huge awkward pauses while I think, so sometimes I'll say something neutral to fill the gap, to at least communicate the fact that I'm interested in having a conversation. I assume that a lot of people do this.

So ditto Del Murder, except it took me about <s>7</s> 9 minutes to type this, and I had to start over <s>twice</s> <s>three times</s> four times.