We should have photoshop contests
I will lend a hand if anyone has any problems...
As for making a smooth edge, the trick is to make sure that you don't pick up any of the background if possible... especially if it is a dark colored item on a light background.
I recomend using different layers for the background and foreground, and use the eraser in brush mode to get rid of the edge. if it is just a rough edge and the color isnt the problem, use the blur tool on it.