Thinking that someone doesn't "look" like a shoplifter might lull you into a false sense of security. Prevent shoplifting by removing as many opportunities to shoplift as possible.
Merchandise: Arrange aisles and displays so that employees have a clear view of a much of the store as possible. Utilize convex mirrors for areas that are blind spots.2 Put less expensive items closer to the door, more expensive items further away. This prevents a shoplifter from being able to grab expensive items and be out the door in a matter of seconds. Put security tags on merchandise that can only be removed at the cash register.
Learn Shoplifting Techniques: Limit the number of items that can be taken into the fitting room. Lock all fitting room doors so that customers must have an employee them. Require your employees to note how many items the person is taking into the fitting room. Shoplifters will sometimes use a fitting room to put on stolen merchandise under their own clothes. Note anyone who seems to be wandering in the store, or who seems to be watching employees and other customers closely. They may be looking for an opportunity to shoplift when no one is watching. Take note of a person wearing a baggy coat, especially if the weather doesn't call for it. They may be hiding stolen merchandise underneath.
Involve Employees: Have your employees greet each customer as they enter the store. A shoplifter is less likely to go through with his crime if they think someone might be able to identify them. Offer bonuses to employees who catch shoplifters and alert security. Let your employees know that shoplifters often work in teams, with one person distracting the employee while the other one shoplifts. Tell your employees avoid distractions and to watch other customers at all times. If you have more than one employee, train them so that only one deals with a dominant customer while the other watches the store floor.