Some images look much better in black and white than they do in colour.
Increasingly photo editing programs are shipping with very good tools for converting to black and white. These allow you to select which portions of an image become black and which become white which is necessary when you want to differentiate between colours which have the same intensity such as green and red values which would, otherwise, be converted to the same shade of gray.
In Photoshop Elements, choose Enhance > Convert to Black and White and select a style from the list at the left of the dialog. These include Infrared, Newspaper, Urban Snapshots, Scenic Landscape, Vivid Landscape and Portraits. While the names suggest the type of image they are well suited to it is a matter of personal preference as to which you use.
Once you have chosen the image type you can select from options at the bottom of the image to adjust the various colours to darker or lighter shades of grey. You can also select the more or less contrast options to adjust the image contrast.