Make sure they are familiar with shoplifting laws. Establish procedures for them to follow if they suspect shoplifting. Make sure you can see everything that goes on in your store. Keep counters low, no more than waist-high. Mount mirrors in corners so there are no blind spots.
Some stores put turnstiles at entrances so the only way out is to pass the checkout counter.
Place expensive items in the center of the store away from exits. Arrange displays so that missing items are easily noticed. Place small items in neat rows or clearly defined patterns. If you must, fasten expensive merchandise and attach alarms. Reverse alternate hangers of hanging garments to prevent grab and runs.