--create the database
CREATE DATABASE NewDB

--create the user from the login
Use NewDB
CREATE USER [domainuser] FOR LOGIN [domainuser]

--To give user SELECT/UPDATE/INSERT/DELETE on all tables
EXEC sp_addrolemember 'db_datareader', 'domainuser'
EXEC sp_addrolemember 'db_datawriter', 'domainuser'

--To give admin permissions
EXEC sp_addrolemember 'db_owner', 'domainuser'

--Using SQL Auth
CREATE LOGIN loginname WITH PASSWORD = 'passw0rd';

--Windows Auth
CREATE LOGIN domainuser FROM WINDOWS;

DECLARE
  @DatabaseName AS NVARCHAR(128),
  @Username AS NVARCHAR(128),
  @Password AS NVARCHAR(128),
  @SQL AS NVARCHAR(MAX)

SELECT
  @DatabaseName = 'YourDatabaseName',
  @Username = 'Username',
  @Password = 'Password'

SET @SQL = 'CREATE DATABASE [' + @DatabaseName + ']'
EXEC (@SQL)

SET @SQL = 'CREATE LOGIN [' + @Username + '] WITH PASSWORD = ''' + @Password + ''''
EXEC (@SQL)

SET @SQL = 'USE ' + @DatabaseName
EXEC (@SQL)

SET @SQL = 'CREATE USER [' + @Username + '] FOR LOGIN [' + @Username + ']'
EXEC (@SQL)

EXEC sp_addrolemember 'db_owner', @username