If I'm just playing low stakes or freerolls I'll play two games at a time, otherwise I just get bored and my mind wanders. If I'm playing to win, I stick to one and it takes up my entire screen - I take notes on absolutely everything about every player: what they go all in with, how they call, what they raise with in what positions (if it's unusual), etc. It helps not only with the games I'm playing, but I've played so many SNGs now that any one game I'll usually already have notes on one or two players, so I know how I can bust them out right at the beginning.