Authentication in WCF restful web service

Question

Hey Programmers!!
I have implemented a WCF restful web service. Which is connected a database for CRUD operations. and I've created a console client to test this web service. Now I have to implement authentication on that web service. I want to use user name password authentication. There should be a sort of header which should be passed with every request from client end. And I want to compare it with user name password from database.  Can anyone suggest me a simple mechanism for this purpose?? I've searched a lot on the internet but all in vain :'(