How to solve a login problem of SQL Server?

Sometimes when we attempting to login the SQL Server 20xx Management Studio, when we type in the correct password, it fails with:

　　"A network-related or instance-specific error occured while establishing a connection to SQL Sercer. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow 　　remote connections. (provider:SQL Network Interface, error:26-Error locating Server /Interface Specified)(.Net SqlClient Data Provider)"

There are two possible ways to solve it:

　　1) a way of cmd command:

　　　　Step 1: Run cmd( as Administrator);

　　　　Step 2: Type in "net start mssqlserver" and press Enter;

　　　　Step 3: Enjoy SQL Server now.

　　2) a way with mouse click:

　　　　Step 1: Right click at the "This computer" icon on your desktop or at the "This computer" tag on the left in any explorer window;

　　　　Step 2: Choose the "Manage" menu;

　　　　Step 3: Double click the "Service" on the function tree;

　　　　Step 4: Find "MSSQLSERVER(SQL Server (MSSQLSERVER))" and right click at it;

　　　　Step 5: Choose start;

　　　　Bingo!

　　Sometimes, the "SQL Server (MSSQLSERVER)" service will not run properly, just start or restart it may solve many problems.

- This is a note I wrote on Aug. 10th, 2015. Many syntax mistakes may occur in the passage, but this is a milestone to me. Keep going!