I am going to develop mobile site with .mobi domain name.
Many content on my .com website may be similar on .mobi website.
How can I tell google that this .mobi is my site only and that is design for mobile visitors.
What I can make sure that I don't come under duplicate content penalty?
Is there any other preconditions I need to make during development of mobile site?
Is it good idea to create .mobi site or it will be good idea to create domain name / mobile sub folder?