Start by understanding the client’s data architecture and prioritizing data cleanliness. Use Power Query to perform data transformation and cleansing before loading it into Power BI consulting. Implement incremental refreshes for large datasets to optimize load times. Use DirectQuery mode for real-time analytics when appropriate. Consultants should also create aggregations for performance improvements on large datasets. Lastly, ensure proper data relationships are set up in the data model to maintain a well-structured, query-efficient system.