The first possibility is off-shoring. The lower your labour costs, the less expensive it is to manufacture a product. Thus if you can move your manufacturing to a lower wage location while preserving quality you will reduce your costs.
The next is looking for efficiencies in the production process. One major area you can look for is reducing or reclaiming waste. How this can be implemented is often industry specific. In the garment industry, it might involve, for example, changes to the way fabric is cut, or thread is used. What is important is reviewing each stage of your manufacturing process to avoid waste of materials and energy.