Make sure that there is rinse aid in the dispenser.
2. Clean the detergent dispenser to ensure it's opening and dispensing correctly.
3. Clear the debris that may be caught under the float assembly located on the bottom of the dishwasher tub and be sure that it can move up and down freely.
4. Run the dishwasher without detergent to ensure the problem isn't caused by the use of too much detergent leaving reside on the dishes.