If your dishes are not getting as clean as they used to, there is probably not enough water getting into the machine. This is usually caused by a broken or worn out water inlet valve. These valves, located behind the lower kick panel, need replacing every 3 to 7 years, depending on water conditions.
Inspect and clean your dishwasher. You don't need to clean the interior of your dishwasher if you use it regularly. If it goes unused for a week or more and begins to mold or smell bad, you can clean it using dishwasher cleaner and deodorizer.
Clean your dishwasher spray arms. Over time, small holes in the spray arms may become clogged with bits of paper, toothpicks, glass, etc. Take a moment to clean out these holes to ensure you're getting the best cleaning ability. Clean your dishwasher filter. If the filter is damaged, replace it to protect the dishwasher's pump and motor seals.