Best Behavior: Don't Interrupt
You're on the phone with a friend and you feel a tug on your free hand that's so forceful, you're sure it's King Kong on the other end. As you know, when your child wants attention, he often insists on having it right now. But your child is old enough to be patient and occupy himself for a brief period of time, and it's fine to have him wait.
Make it Happen: Explain that when you're talking to someone else, it's not okay to interrupt unless it's critical (someone is hurt or he has to go to the potty immediately). For any other less-important intrusions, firmly tell him, "Mommy is on the phone. Play with your blocks while I finish talking and I'll be right there." Then follow through when you're done with the call by thanking him for being patient and giving him your undivided attention.