Final answer:
The consultant should sync contact and custom objects with Data Stream and send from a Synchronized Data Extension with Salesforce Email Send in order to use Salesforce Custom object data for segmenting and personalization.
Step-by-step explanation:
The consultant should approach this requirement by syncing contact and custom objects with Data Stream and sending from a Synchronized Data Extension with Salesforce Email Send.
This can be done by ensuring there is a lookup relationship to a contact or lead record.
By doing this, the user in the Marketing Cloud can segment and personalize based on the custom object data