My dishwasher is not cleaning properly.
Do not attempt service or replace parts of the appliance unless referred to in the owner's manual. Follow all safety precautions provided in the owner's manual.
Detergent/Rinse Agent  
Use powder detergent for best wash and rinse results. Do not put detergent into the dispenser until you are ready to wash dishes. Powder detergent needs to be kept fresh and dry. It can become stale as it ages or when stored in damp areas. Do not store it under the sink, because this can be a moist area. Before using powder detergent shake the container. If the detergent has clumped together, it may be too old and will not wash well, since old detergent loses power and often will not dissolve. If your dishes are often heavily soiled, you may need to use detergent with a higher phosphate level, if it is available in your area.  
 
Water hardness plays a determining role in the amount of detergent needed. Insufficient or excessive detergent will affect cleanability. Generally, soft water requires less detergent while hard water requires more. Read the usage recommendations on the detergent container and in the dishwasher's Owner's Manual.  
 
Spots on glasses or silverware may indicate a hard water condition. Try slightly increasing the amount of extra detergent and/or rinse agent. If you have hard water, make sure water is actually entering the dishwasher. If it is not, the minerals in the water may have plugged the water inlet valve. In most cases, the valve will need to be replaced.  
 
If you have a water softener, run the dishwasher only when the softener is full. If the dishwasher is run after most of the soft water supply has been depleted, the dishes will not get clean, and they may look even dirtier than when they were put in.  
 
Use a rinse agent whenever possible. Rinse aids allow water to flow off dishes quicker than usual. This lessens water spotting and also makes drying faster.  
 
Water Temperature  
Your water heater should be set no lower than 120° F to obtain the best results from your dishwasher and detergent. Most detergents today will not properly dissolve if the water temperature is too low. The optimum temperature is 140° F. Run the hot water at the kitchen sink before starting the dishwasher to purge cooled water from the supply line or use the temperature boost option (on some models) to increase the water temperature.  
 
Also, check your home water pressure. Water pressure should be 20 - 120 per square inch (PSI) for optimal results.  
 
Obstruction  
If the spray arm holes are blocked with any type of debris (broken glass, seeds, plastic, etc.) the water will not be able to spray properly. Remove any debris from the spray arms.  
 
If a spray arm is stuck in one position due to an obstruction, it will disrupt proper water flow inside the dishwasher during use. Rearrange how the dishes are loaded. Make sure the spray arms can spin freely and the wash tower is not obstructed. (Avoid nesting items.)  
 
Wash Cycle  
Heavily soiled dishes may need additional wash time. Make sure you choose the appropriate wash cycle for the dishes being washed. Different wash cycles have longer or shorter wash times.