Don't fill up the CMDB will obsolete Configuration Items(CIs).
Ensure each Configuration Item(CI) has a single source of truth.
Do not synchronize AD Group objects unless required
Ensure to select the option ‘Do not write null values for properties not set in Active Directory’.
Use LDAP filters to only import relevant types of objects.
When implementing multiple AD connectors stagger the schedule so they don’t all run at the same time and ensure they do not run during Backup or other Maintenance Windows
AD Connector Deletion
Line Manger and User must be imported using the same connector
Mapping AD Connector Properties to Service Manager http://technet.microsoft.com/en-us/library/hh524307.aspxMihai Sarbulescu has an excellent blog covering AD connectors tweaks http://blogs.technet.com/b/mihai/archive/2013/08/14/tweaking-the-ad-and-cm-connectors-in-service-manager-2012.aspx
The Service Manager Product Group has also posted an excellent blog improving AD Connector performancehttp://blogs.technet.com/b/servicemanager/archive/2014/03/19/improving-ad-connector-performance.aspx