Keep one in the shower filled with a mixture of half vinegar and half Dawn dishsoap. Use it to wipe down the shower while you are in there and your shower will always be clean. I keep hearing that this is the magic formula!
Once a month, add a cup of Distilled White Vinegar and a cup of baking soda during the HOT cleaning cycle. pour them directly into the drum. Then, add about ½ cup of vinegar and ½ cup of baking soda into the detergent dispenser.