The most important thing to remember is that there's nothing wrong with taking a break, especially if your boredom is making you too loose.

If it's just ring games, then having more tables open at a time may help. I play a small number of tables but try to watch each of them, and then if I see something interesting unfolding, I'll eye it carefully and try to guess each player's hand and make notes if anything gets revealed. I may even start talking out loud if nobody's around. "Really? That's a bold raise; maybe you want to protect your hand and get him out of a draw? Oh hey, he called. What will you do now?..."

I also like having background music playing from somewhere, although people have said that may be more of a distraction than it's worth.