Over portioning hurts the restaurant and customers. The next time they visit your establishment they will be disappointed and won't return, thinking they are not getting the value for their money that they received the last time they visited. Ownership being on premises as much as possible and keeping constant contact with all aspects of operation, even on a minimal basis. The thing I feel has the most influence on controlling food cost in my restaurant is training of the managers and crew. Properly recording waste, tracking employee meals, and product rotation are all often overlooked in the process of initial training of employees.
Security is another important factor.
How easy it is to throw a case of meat under the trash and stick it in your vehicle while you're outside. Staying on top of these things will make a definate impact on food costs. Communication is another impact. I have started doing daily inventories on my problem items, and I am zooming in on where the problems are starting. Educate employees on what each product costs, put it in terms of things that they can compare to such as a case of lettuce costs as much as a tank of gas.