New installation of SQL Server and solving the login error 18456

If you have just recently installed SQL Server onto your database server and have trouble logging in, changes are you've run into error 18456.

This error, as documented on MSDN, is related to login issues with the given username and password. Usually, this problem is solved by checking that you have indeed enabled SQL Server authentication on the server. The latest SQL Server versions only install with Windows authentication enabled by default (which is good), but for many applications, you will need to add support for SQL authentication.

You will get the error 18456 if you forgot to enable SQL authentication on the server.