stopping barking?

What do you guys do to stop your dogs from barking, if anything? I have wondered if a dog whistle would do anything to startle her and might make her stop but I haven't tried it yet. It's mainly Peaches that I'm having problems with as if she even thinks she sees something or someone outside, she just goes nuts and won't shut up unless I chase after her. Then she gets the other two started :(
She even starts to bark if she hears a doorbell on TV because she thinks it's ours and runs to the door barking like there's no tomorrow. I don't mind if she barks some but sometimes it's just rediculous and she doesn't want to shut up. Any advice is much appreciated :)