I don't call my dog anything. I just repeat the command softly and then correct as needed. A simple snap of the fingers, whistle or look will cause my great dog to do what's he's supposed to. He's only 6 months old too
I think most people forget that when you say a command to a dog you should never say the command harshly.. this creates a negative connection in the dog's mind with the connection. So next you want Fido to sit, don't yell the command, say it in a normal, calm voice.