There is no easy way. you need to create a custom code. It can be custom web app, using javascript or plugins. I will be do it using plugins.
This will give some starting point http://www.thuta.info/2010/06/clone-record-in-crm-using.html.
I hope this helps.
If you find this post helpful then please "Vote as Helpful" and "Mark As Answer". Amreek Singh Senior CRM Consultant CDC Praxa Sydney, Australia
http://mscrmshop.blogspot.com
http://crm2011usersettings.codeplex.com