Creating a Black and White image with Selective Coloring

• Open your image
• Make sure your Layers palette is open (Window -> Layers)
• Click on the locked Background Layer just so it's highlighted
• Right Click on it and select "Duplicate Layer"
• With the Background Copy Layer highlighted follow the steps to turn it b&w (Image -> Adjustments -> Desaturate)
• Now with your Eraser tool just Erase the parts you want in color. If you want large parts of an image to be in color use the magnetic lasso to make the selection and then hit the Delete key on your keyboard