What strategies should you follow to accomplish your customer's goals?

One of the most powerful tools to measure sales at retail stores is to use Facebook offline events. With Offline Conversion Tracking, you can track when transactions occur in a physical business location and other offline channel, after people see or engage with a Facebook ad. 

Use precise timestamps, including minutes and seconds to track multiple purchases.

Use actual transaction value to see the most accurate event values on a dashboard.

Use Order ID's or item number to include multiple items within a single transaction.

So the best strategy is to use offline events to better understand how Facebook marketing campaigns affect the retail stores.