
Create a levels adjustment layer; bring the highlights and shadows in if necessary
To create an adjustment layer; from the menu select ‘Layer’|‘New Adjustment Layer’|‘Levels’
Create a channel mixer adjustment layer; ‘Layer’|‘New Adjustment Layer’|‘Channel Mixer’

When the dialog box appears, click the Monochrome check box

Experiment with the values, as a general rule they should equal 100%

Add a curves adjustment layer, this will allow you to fine tune the image output

To make the sky more dramatic, add a levels adjustment layer.
Change the blend mode to linear burn

Select the brush tool, make sure black is the foreground color. Select a soft edge brush that is about 400 pixels. Set the opacity to 40%, brush to reveal the foreground

If you want to make further adjustments, you can do so using the ‘adjustment layers’ created earlier, that haven’t changed the original image or other layers. Use the visibility (the eye) to see what effect a layer has on the image. Once your happy with the conversion, flatten the image, select ‘Layer’|‘Flatten Image’ and enjoy your custom black and white conversion