Situation: developer workstations that typically just use the client tools to connect to other non-local sql servers. However, there are rare times that having the full version of sql server to do local development will be beneficial. In an effort to not waste system resources running sql server all the time I would like to know the best way to "turn it off" while still allowing usage of client tools (management studio, etc).
You may need to access SQL Server Configuration from the Start menu by selecting Microsoft SQL Server and then Configuration Tools, and then follow Thomas' path.
You can also configure those services so that they don't start automatically. I have mine set on "Manual", so if I want to use the SQL Server server, I just start the service. Ditto for SSIS, SSAS, SSRS, etc.
Since I have two versions of SQL Server running on my development machine, I don't want all of this stuff eating up my resources.
I'm a fan of PowerShell for this. Depending on the details of what you want to accomplish:
Stop a particular instance:
Stop-Service 'MSSQL$InstanceName' -Force
or to stop all SQL related services.
Stop-Service *SQL* -Force
or create a double-clickable script to toggle the state: http://orionseven.com/blog/2010/10/18/starting-and-stopping-sql-server-with-windows-powershell-2-0/