If I'm out at a restaurant or something, I silence it the moment I sit down like I do at movie theaters-there for I don't check if I don't hear or see it ringing. I find it immensely rude when people's phones are ringing and being answered in restaurants. If I'm on another call, I WILL look at who it is, but generally I'll keep talking to the original person unless its an expected/important call. If I was on a call with a friend and the SO called, I'd click over and see what's up. If its something quick, make the exchange brief and click back over, if its long I tell her I'll call her back in a few.