CRM consultants ensure that the system delivers value to users ie its configured to suit the way your business works, integrating with other tools you are using.
a consultant helps their client understand how they would use CRM as a strategy to support their business objectives – this involves understanding their current capabilities, mapping their desired future state, and then identifying (and possibly filling) their capability gap.
The consultancy would involve the 5 core elements of CRM – strategy, data, technology, process and culture – so the workstreams would include projects/tasks such as business change, campaign deployment, data analysis, systems requirements, etc.
However, note that this is our interpretation as technology neutral CRM consultants. A CRM software sales firm (such as SAP or MS Dynamics) might have a different definition – for them a CRM consultant might be “teach our clients how to use our products”.