Tighten everything properly. Check chainline. Give bike to mechanic.
First one - http://www.sheldonbrown.com/creaks.html Second one - http://www.sheldonbrown.com/chainline.html Third one - Take it to your local bike shop if 1 & 2 don't seem to improve things.
Can I also suggest that you look into this to expand your technical knowledge of bikes - great starting point for learning the basics and more. http://www.wiggle.co.uk/haynes-bike-book
@Aroogah started
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First one - http://www.sheldonbrown.com/creaks.html
Second one - http://www.sheldonbrown.com/chainline.html
Third one - Take it to your local bike shop if 1 & 2 don't seem to improve things.
Can I also suggest that you look into this to expand your technical knowledge of bikes - great starting point for learning the basics and more. http://www.wiggle.co.uk/haynes-bike-book