Best way to change Service Account in SQL Server

If you need to change the service account for SQL Server service or SQL Server Agent service for that matter, use SQL Server Configuration Manager. Though you can also use Services(Administrative Tools->Services) to accomplish the same thing, the recommended method is to use SQL Server Configuration Manager. It is because SQL Server Configuration Manager will automatically grant all the required permissions and rights to the new account. If you use the Services add-in to change service account, you might have to add some additional permissions and rights to the new account manually.