This is much more sophisticated than the Black and White conversion found in older versions of Photoshop, and will allow you to increase or decrease the levels of black and white for a particular colour.
It is also a great way to create duotone effects.
1. Open a coloured photograph of your choice in Photoshop CS3.
2. From the Image menu, select Adjustments > Black & White
3. The new much improved Photoshop Black & White conversion settings window will appear. Make sure the "Preview" checkbox is selected, so you can see any adjustments live in the document.
4. If you just want Photoshop to convert the image using its own settings, click the "Auto" button. But for this tutorial, we will create our own custom settings. Drag the "Blues" slider towards the left to make the blue tones in the image darken. This will create a darker sky with more pronounced cloud contrast. this totally changes the image's mood.
5. Dragging the slider to the opposite direction will lighten the blue tones of your image, making the sky almost disappear, as shown below:
6. If you want to find out the colour of a particular part of the image (in this case, the bricks on the church) mouse over the image. The cursor will change to an eyedropper. Click once in the church and notice how the yellow slider becomes active: the numeric value is highlighted, and a bold black outline appears around the yellow colour chip as shown below.
7. You can also click and hold down the mouse to reveal the sliders inside the image itself. The eyedropper cursor will change to a hand icon with arrows at each side.
8. You can now drag left or right to increase or decrease black and white levels, Hoses changes will be mirrored in the sliders below.
9. To add a duotone effect, click on the "Tint" checkbox at the bottom of the window. This will open up the Hue and Saturation sliders .Choose a tint from the Hue slider and then use the Saturation slider to increase or decrease the amount of colour to add to the image.
10. The finished image.
More Tutorials: 
