There are plenty of ways to convert your images to black & white in Photoshop but by using a Gradient Map you'll have more control of how your final image will look.
Step 1: Adjust your colour image
Before you begin playing with a Gradient Map you may need to adjust the image. To do this, click on the black & white circle at the bottom of the Layers Palette and you'll find a long list of adjustments you can make to your layer.
The beauty of creating an adjustment layer means you can simply double-click on the black & white circle on each individual adjustment layer to reopen the adjustment window to make any changes.
Step 2: Gradient Map
Make sure your foreground colour's set to black and the background to white. Go back to the Adjustment Layer drop-down menu at the bottom of the Layers Palette and select Gradient Map. When the Gradient Map Adjust Layer window opens your image will automatically be converted to monochrome. Click on the box
that's filled with the gradient (where the red arrow is pointing) and the Gradient Editor window opens. Now you can adjust the sliders found on the gradient bar to create the tones you think are appropriate for your image.
Both the bottom and top sliders can be moved by clicking and dragging them or by inputting a figure between 1 and 100 into the Location box.
The top sliders let you adjust the opacity of the gradient while the bottom slider, the one we are going to use, lets you adjust the colour of the gradient. If you want to add more points to the top or bottom sliders simply click along the top or bottom edge (where the arrows are).
To adjust the colour of the point you're adding place your mouse cursor over the gradient so a Pipette tool appears and click on the colour you want to add.
Also, the smaller points located between each stopper can be adjusted to alter the gradient slightly.