Describe the problem. Then tell them how you managed to solve it. Go into detail as to the process you used. Highlight how you used good judgment.
Example: I was responsible for reorganizing the shipping orders in our company. The company had received many complaints about receiving wrong orders. I examined the order file system, truck routes, and packaging facilities. I found that the file system did not match the system used in the packaging facilities. I fixed the discrepancies and created a new color-coded system to ensure that our customers received their correct orders. My new system proved more efficient by saving the company more time and money.