I am wondering where can I find some steps to create a staging for EE2 ?
If you know how to create a production or development server for EE2, you can create a staging server... if you don't know how to create a development or production server then go find that out first.
There is no elegant fix for this - how you solve it very much depends on what you use the CMS for and what sort of changes you plan on making.
This is not an EE issue specifically - you'd have the exact same issue with any database driven CMS.
If you give some more info on what kind of environment you want the staging server for, maybe there is scope for a more complete answer, but for the generic concept this is it.