create another web application using a copy of the same content database

Hi All,

I have a backup of content database (*.bak) file and one of the web application in my farm is currently running it. Now, I would like to create another web application using a copy of the same content database. 

I went through some articles on the internet that says using -AssignNewDatabaseId and restoring worked for them, for others it didn't. 

What would be the best approach?

My content db size is around 30 GB

Any pointers/links would be really appreciated.