Get a headpiece
Whether you swear by bluetooth or you like the free set of earphones that came with your iPhone, make sure you're not caught holding your phone. Having your hands free means you can write or type notes. And, with an earpiece closer to your eardrum, you won't miss what the caller's saying.
If you're near your machine, nothing may be worse that someone popping in on Google chat with the annoying sound effects that come with it. Or, you don't want an iTunes song starting up accidentally. Just press the mute button to avoid this.
Schedule calls in succession
I try my best to have all my phone time on one day of the week. This way, I'll make sure that my settings are ideal for taking the call (in my office, door closed, mute button pressed) for an extended amount of time and will decrease the prep time needed to take a call. I'll also be mentally in 'call mode' and ready to speak to the person I'm phoning.
Always take the call
Peter Shankman does this, and he's done well for himself. Then again, Tim Ferris never does and he's done okay, too. So, it depends upon your work, but I'd side with Shankman. Just this week, answering the phone has led to me scheduling a book appearance, a press interview and signing a new partner. Sure, they could have left messages, but by appearing available and excited, I like to think it's better for business. Just be ready when you say hello.
If your computer's on so you can take notes, shut down the Internet. This isn't the time to be looking at Facebook photos or catching up on blogs. It's game time. Time for business. You don't want to blow something great just because you were too absorbed in someone's tweets. That'll be there after you finish the call and sign a new client, which will make for a better status update later anyway.
Photo credit: EverJean from Flickr