How to copy an existing permission level in SharePoint 2010

·         Verify that you have one of the following administrative credentials

o   You are a member of the Administrators group for the site collection.

o   You are a member of the Owners group for the site.

o   You have the Manage Permissions permission.

·         On the Site Settings page, under Users and Permissions, click Site permissions.

·         In the Manage section of the ribbon, click Permission Levels.

·         In the list of permission levels, click the name of the permission level you want to copy.

·         At the bottom of the page, click Copy Permission Level.

·         On the Copy Permission Level page, in the Name field, type a name for the new permission level.

·         In the Description field, type a description for the new permission level.

·         In the list of permissions, select or clear the check boxes to add permissions to or remove permissions from the permission level.

·         Click Create.

Ref: http://technet.microsoft.com/en-us/library/cc263239.aspx#section3