Check the water and detergent
A dishwasher's failure to clean dishes doesn't necessarily mean something is broken. Start your troubleshooting by checking the water temperature in the sink. If it isn't hitting at least 110 Fahrenheit, adjust your water heater to give you hotter water. Check your detergent as well to make sure you've chosen the right detergent for your local water's level of hardness. The way you load the dishwasher can also make a difference in how well it cleans.
Inspect the detergent dispenser
Check after running a load of dishes to make sure your detergent dispenser actually opened the way it should during the cycle. If the dispenser doesn't open correctly, if it's cracked or if the latch is broken, you may need to replace the dispenser assembly. This is one of many dishwasher parts you can find easily available at Sears PartsDirect.
Clear the chopper blade area
If your dishes aren't getting clean and you hear an odd grinding noise when the dishwasher is operating, you may need to do a little dishwasher repair on the chopper blade. The chopper blade rests under the lower spray arm and dishwasher sump, and it can be damaged if a hard item becomes lodged inside it. Disassemble the lower spray arm and clear out any debris, checking for damage to any parts along the way.