Checklist: Before extending the schema

Step Reference
Carefully plan the changes you want to make. The Active Directory Programmer's Guide at the Microsoft Web site
Verify that these changes are really necessary. When to extend the schema
Fully understand the issues involved in extending the schema. Issues in extending the schema
Fully understand how these new objects and attributes will be managed. Issues in extending the schema
Determine the proper names for any new schema objects. Schema object names
Obtain a valid object identifier for each new schema object. Obtaining valid object identifiers
Understand single master operations. Single master operations
Join the Schema Admins group. Add a member to the Schema Admins group
Install the Active Directory Schema snap-in. Install the Active Directory Schema snap-in
Locate the current schema master. Identify the schema master
Enable schema modifications on that computer. Enable this computer to extend the schema
Verify that any previous schema changes have been fully replicated to all domain controllers. Active Directory support tools
If possible, when testing unproven schema changes, test them in a separate test forest.
Review the information about extending the schema. Extending the schema;
The Active Directory Programmer's Guide at the Microsoft Web site