Hi,
There are a few ways of doing this.
There is a choice of 4 templates and mobile version could be any one of them depending on the browser used by the mobile. The techniques either mimic (M) the browser or force (F) the site to a choice.
1) M User agent switcher
www.mobilejoomla.com/documentation/13-development/52-user-agent-switching.html
2) F Using a subdomain
3) F adding a parameter to the url
4) F using the select markup module
5) F using the mobile always plugin
6) M modify headers
addons.mozilla.org/en-US/firefox/addon/modify-headers/
Each has it's advantages and disadvantages.
Some set cookies, so you will sometimes need to clear cookies (session and domain) and cache when you change from one mobile version to another.
If your site is in development and you are the only visitor, then I recommend (5) as you can force the site to use a particular template.
1 and 6 can be used to see which template a specific phone will get when it visits a site.
You can define your own user agents. Visit
www.mobilejoomla.com/uatest.php to see the string for the browser you are currently using.
You use them by selecting a user agent from the drop down and then visiting the site (or refreshing the screen if you are already there). Bear in mind that the firefox screen is bigger than the phone, but you could use the firefox web developer toolbar to resize it.
2 has been the subject of many items in the forum.
Examples from the site I maintain are :
imode.boynhillbaptist.org.uk/
iphone.boynhillbaptist.org.uk/
pda.boynhillbaptist.org.uk/
wap.boynhillbaptist.org.uk/
www.boynhillbaptist.org.uk/ (default, which recognises browsers and shows appropriate template).
I'm just using these as examples so you can see what it looks like. The site is not on the current version of MJ as I customised it and it was working well enough.
3) add ?device= to the url.
www.mobilejoomla.com/forum.html?device=chtml
www.mobilejoomla.com/forum.html?device=desktop
www.mobilejoomla.com/forum.html?device=iphone
www.mobilejoomla.com/forum.html?device=wml
www.mobilejoomla.com/forum.html?device=xhtml
4) As delivered the "Select Markup" module shows just in the mobile templates and has a choice of mobile or standard (desktop). You need to make a copy of this module so you can publish it to the footer of the normal template for the site (as seen by the desktop). You will find extra parameters in here so you can switch to other templates.
5) The "Mobile always" plugin has a parameter which can force the site to only display using a specific template:
Auto (default) uses the template for the browser. This is true even if you disable the plugin.
iphone (iphone/ipod) and ipad depending on ipad support setting in components > Mobile Joomla > Settings > iphone
xhtml-mp (WAP2/PDA) most smartphones including Blackberrys.
chtml(I-mode)
wml (WAP)
Hope that helps.