If you want to enhance those beautiful brown eyes, start experimenting with blue eyeshadow colours as they are in the opposite colour family to brown. It sounds odd, however wearing a contrasting colour will really help to make your eyes smoulder. Trust me!
To give yourself a variety of different looks, invest in a good eye shadow palette. I recommend the Estée Lauder Arctic Zinc (£27.00 Boots / $36.00 esteelauder.com).