Matching and Duplicate Rules
Ensure Matching Rules are set by launching the Matching Rules feature from the Lane Four launcher.
Matching rules represent the fields which will be used to connect leads with accounts, or manage duplicate scenarios between leads, contacts and accounts.
Create Duplicate Rules for Accounts, Leads and Contacts.Setup > Data.com Administration > Duplicate Management > Duplicate Rules
Ensure Duplicate Rules are in the expected order by selecting an object from the view dropdown list:
You can find more information on Salesforce Duplicate Management here