Don't leave the detergent cup open when you start a load. It comes with a little door for a reason. If the door is left open, the detergent washes into the bottom of the appliance and goes down the drain without even touching your dishes. Door won't close? You may be using too much detergent. Be sure to check the label for the proper amount.
Adding extra detergent to get dishes extra clean may seem tempting, but restrain yourself. That little extra won't make your dishes any cleaner and may leave a film on the dishes. If your dishes aren't getting as clean as you like, it may be the placement of your dishes or the brand of detergent, not the amount.
You may have seen that commercial where the lady puts a pan full of lasagna into a dishwasher and the pan comes out sparkling clean. In real life, everything in the dishwasher would be covered in little flecks of lasagna. Plus, the food trap would get clogged and the dishwasher would probably overflow. Dishwashers may be able to clean an amazing amount of grime, but there is a limit to how much they can take. Scrape all plates and pans with a plastic spatula before putting them into your dishwasher just to be on the safe side.
If you have hard water, your dishes are going to be spottier than a dalmatian. Don't just wipe away the problem after every load, fix the problem. Add a boosting agent or hard water spot remover. These products can be found on the same isle as dishwasher detergent.
If you are putting more than one plate in each slot or stacking cups, then you're overcrowding your dishes. Not only will they not wash properly, but they also may clang together and chip or break. Always give your items enough room so they don't touch.
No matter if it's pot handles, spoons, tongs or other items, don't let them hang below the bottom rack. The sprayer can get hung up on the item, which will not only lead to dirty dishes, but also may cause your dishwasher to break down.
Ignoring hard water can do more than just leave spots on your dishes, it can also build up in the mechanisms of the dishwasher, leading to repairs. One way to avoid spots is by adding two teaspoons of Borax or baking soda to your regular dishwasher detergent once a month.
This may be common sense, but I've know people to try this, so I'm going to include not using dishwashing liquid (or any other type of cleanser) in a dishwasher as a no-no. Only use cleansers that are meant for dishwashers. Dishwashing liquid will bubble up and overflow. Then you'll have dirty dishes and a flooded floor.
The best temperature for washing your dishes is 120 degrees Fahrenheit (48.9 Celsius). If your dishwasher doesn't have a heating element, or you don't use the water heating option, check to make sure that your water heater is set to at least 120 degrees.