How to convert contacts to leads? screencast please

The help docs talk about Converting leads to contacts but what about the other way around?

You meet someone... they are just a contact... they eventually turn into a lead for more business... how do you convert them from a contact to a lead? Do I have to export that contact(s) as XLS and then reimport them as Leads?!

Please advise as we've a number of these... A screencast would be most appreciated!

thanks!
Dennis
Dennis Daniels