Create your mobile template just like the main site but probably without the side menu.
You may wish to have an auto CSS redirect although we prefer to simply include an additional CSS style sheet that overwrites the necessary tags to make the mobile site display correctly.
Add the following code into your main site template and this will redirect to another page with the same name except for an 'm' in front of the name.
Full list of special template TAGs
Build the main site again with the redirect script in.
Then go the the setup screen.
Select the new mobile template.
Select the home page name and A1 or menu name so that you don't overwrite the index page
Add an m to the prefix box. This should be the same as you added to the template redirect.
Now just upload the mobile site next to the main site. The different page names will allow them to work together.
Look at our example here and just add an m before each page to see the mobile site.