Upgrade to Joomla v 3

Hi,
I have a hot business template on version 2.5 of Joomla. I now wish to upgrade to version 3. What is the best method please
Thanks
Hugh

You can upgrade joomla by going to Joomla!Update in admin menu, then go to its options. For server select 'Short term Support', information to upgrade to 3 should when you return to dashboard. After that you need to replace template by overwriting template files with files of new template version (for j3) you can download for our site.
You need to skip files you changed, probably teamplte_css.css