Custom Authentication & Authorization

Hi Everyone,
I have an Asp.Net MVC 3 (it's not important) and i don't like to use another Database(Asp.Net Database) for authentication and authorization, i only want some more filed and relations in some tables of Asp.Net Database so i think the best solution is customizing Authentication and Authorization,
How can i do it(please help with some code or sample or a good resource)?


*I'm a little new to Asp.Net


Thanks

...