Go to the dish soap section of your supermarket and you will find several good products for this purpose. Follow directions on the container.
Another thing you can do is open the door after the last rinse fills up and pour in 1/2 cup white vinegar. It is hard to remember to do this. You might want to set a time clock.
When your dishwasher is running, try not to turn on water in the rest of your home such as take a shower.