Assuming that you are using windows auth with a login 'domain\user' that has already been created.
--create the database
CREATE DATABASE NewDB
--create the user from the login
Use NewDB
CREATE USER [domain\user] FOR LOGIN [domain\user]
--To give user SELECT/UPDATE/INSERT/DELETE on all tables
EXEC sp_addrolemember 'db_datareader', 'domain\user'
EXEC sp_addrolemember 'db_datawriter', 'domain\user'
Alternatively to give the user admin over the database, replace the last two lines with.
--To give admin permissions
EXEC sp_addrolemember 'db_owner', 'domain\user'
CREATE DATABASE
also has many options which you might need that can be found on BOL.
http://msdn.microsoft.com/en-us/library/ms176061.aspx
If you need to create a login
also then you will need the following before creating the USER
on your database.
--Using SQL Auth
CREATE LOGIN loginname WITH PASSWORD = 'passw0rd';
--Windows Auth
CREATE LOGIN domain\user FROM WINDOWS;