Important: Take whole site backup (source, database and others if any) before you start any step below.
If your new domain on the same server than
just move your source file from domain1 folder to domain2 folder and in qa_options change site_url field with your new domain Site URL. This you can avoide to do by changing it from Admin > Generral settings before you move your source code. This is a trick. So before you moving your source you are defining new domain Site URL in DB :) so you don't have to change it manually.
If you are moving server also than you need to take db backup and source file.
Than create db and import sql to that db.
Assign user to db for access
place source file to your new domain / server folder
Than update you qa-config file
>> You can avoid updating qa-config file by creating database and user with the same name you have already in qa-config.
Hope this will helps you :)