The following are some best practices of the MIM portal:
Minimize the use of dynamic nesting and the use of negative (NOT) conditions in sets and groups. A good rule of thumb is to stay under five NOTs.
Disable the verbose tracing of MIM Service when not needed.
Be aware that exposing self-service reset internal and external could be a Denial of Service endpoint if you have Active Directory configured to lock out.
Back up custom workflow code and pages and manage them as you would any production source code.
Do not delete the default workflows that come with the product.
Keep an eye on expired portal requests. If you see requests building up beyond the retention time (default 30 days), then you may need to run the SQL job FIM_DeleteExpiredSystemObjectsJob.