Check to make sure you've plugged in the unit and that electricity is getting to your dishwasher. Flip a circuit breaker if the machine has been working steadily and then suddenly stops working.
Turn the dial to the starting position. Make sure that you've latched the door securely if the machine doesn't start. If it still does not start, call a technician.
Look for the supply valve beneath either the dishwasher or the sink if the appliance does not fill with water. Turn the supply valve on if it is off. If the supply valve is in the "On" position, open the door to the dishwasher and remove the cylinder-shaped float switch cover. Jiggle the float a few times and replace the cover. Replace the switch on the front of the dishwasher if the float switch is broken.
Replace the gasket---the rubber strip extending around the inside edge of the door---of an older dishwasher if the problem is water leaking onto the floor. Tighten the water valve and hose clamps for new machines if they leak. Try jiggling the float switch as you would if the machine was not filling with water.
Check that the sprayer arm is not hitting any cookware if the dishwasher starts making a strange sound. Move items so they don't impede the sprayer arm. If the sprayer arm is not hitting anything, raise the dishwasher on leveling legs to see if the motor mount has come loose and is striking the floor.
Install a filter to keep iron from contaminating the water if you notice rust stains on your dishwasher. You may also need to install a water softener to rid your water of iron content.
Inspect the water inlet valve solenoid when the dishwasher either won't fill or overfills. Turn off the power supply, remove the access panel and look for the water supply connection. Test the solenoid with a continuity tester.