To me, I think, it's the best to shut up. When you have nothing to say, my contention is that, rather than making a mess out of it, by spilling out your ignorance for everyone to see, you'll be wiser by just not opening your mouth.
Another good thing to do would be to plan your next move or next thing to say. I've seen people taking the not-knowing-when-to-shut-up to a point where they fill fuss into the situation and make it go awry. On reiterating, I'd like to say that you have it all in your hands!
P.S. I'd not be surprised if someone would use the comment space to say,"Shut up."
P.P.S. No. I'm not done yet.
