A number of useful stored procedures related to users and roles within databases.
EXEC sp_HelpSrvRoleMember EXEC sp_HelpLogins EXEC sp_HelpUser EXEC sp_HelProtect EXEC sp_HelpRoleMember
Create a login (QuickRef).
CREATE LOGIN [(DOMAIN\)User] (FROM WINDOWS) WITH (PASSWORD = 'A34esdjdawki^tW4', ) DEFAULT_DATABASE = [DatabaseName]