We have to see what modules are installed.
But in General:
1. To make a backup of the database and website
2. To export through the admin panel all the database fields (you can, if you understand only those that You need)
3. To set oxtar
4. Install modules that were installed and the template
5. To import the database
And. in each case, can be private nuances...
In General, oxtar and clean therefore differ not very much.. Just oxtar added a few features (file system)... And the localization of their own.