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Finally, and this can be a bit more advanced for some shops. Authorization rights should be as discreet as possible and should surround real functional behaviours.
Typical Role-Based Security (RBS) approaches tend to have a Group mentality. From a security perspective this is not the best pattern. Instead of 'Groups' like 'User Manager', try breaking it down further (Ex. Create User, Authorize User, Elevate/Revoke access rights, etc...). This can have a little more overhead in terms of administration, but this gives you the flexibility to only assign rights that are actually needed by the larger admin group. If access is compromised at least they may not get all rights.
I like to wrap this in Code Access Security (CAS) permissions supported by .NET and Java, but that is beyond the scope of this answer. One more thing... in one app, admins cannot manage change other admin accounts, or make a users an admin. That can only be done via a locked down client which only a couple people can access.