Add credentials & set a specific role for a database How can we add login credentials &amp; roles for a particular database?

There is ServerObject,replication &amp; management folders in MS SQLmanagement studio. What's the significance of these folders?

How can we add roles in MS SQLmanagement studio not for a particular database?

What are the main things that we should give more care when creating a database?
See the Database Security Tutorial on ToadWorld (originally SQLServerPedia)