Fill the sink half full of water and add 2 cups of vinegar. This is going to be where your dishwasher bits are soaking while you clean up around the walls and base. If you don’t have vinegar, consider the following:
- Lemonade drink mix or lemon-flavored Kool-Aid mix. (Don’t use strong colors that might stain. There is no need to add the sugar.)
- Lemon juice
- A dishwasher cleaning product
Remove the holders and racks. The two “shelves” of the dishwasher should be removed, along with the utensil holder and any other pieces that aren’t a part of the racks. If they’re small, place them into your vinegar-water sink for cleaning. If they don’t fit, wipe them down with a rag damp with the same vinegar solution.
- Check for food bits! If any are stuck on, use a toothpick or similar small, sharp tool to pry away at what’s been caked on.
Clear any debris out of the holes in spinning arms. Look to make sure all the holes are open so that water can run through them freely. If you have this problem, those holes will need to cleaned in order for your dishwasher to run efficiently. Use fine pointed or needle-nose pliers if you have some; otherwise, try a toothpick or something similar. Take care not to scratch anything if you’re using a tool with a metal point. Remember to take your time and be careful.
- If these holes are very small, bend a fine wire with a tiny hook on one end. Thread the wire through the opening most distal from the center of the arm. Each time you do this a small amount of debris will come out.
- Another option is to drill a much larger hole at the end of the arm. Run the washer to eject the matter, then plug the bigger hole with a stainless steel screw.
Wipe around the edges of the door and around the gasket. This space doesn’t get washed during the dishwasher cycle. Use a damp cloth and the vinegar solution (or, if you like, a bit of mild spray cleaner). An old toothbrush or other soft, household brush can help get into corners and up under the gasket, too.
- Don’t forget under the bottom of the door! In some dishwashers, this is a dead spot where water doesn’t go, so it can accumulate debris. Wipe this off with your vinegar rag. If anything is caked on, bust out your scrub brush as necessary.
Remove mildew or mold with bleach. Run a separate cycle from any acid cleaners you have used and never mix bleach with other cleaners or with dishwasher detergent. Bleach is a very strong chemical, both on you and on your dishwasher, so use it sparingly and only when necessary.
- If mold and mildew is a problem, leave the dishwasher loosely open for a while after each cycle to allow it to dry out.
- Avoid using bleach and detergents containing bleach if your dishwasher has a stainless steel interior or door.
Tackle rust stains. If your water has a lot of iron or rust in it, rust may be beyond your control. If possible, address the problem at its source. If the problem isn’t rusty pipes, water softeners can remove a limited amount of iron from water but they mostly work by exchanging minerals that are hard to clean off surfaces for salts that are relatively easy to clean. Filters do exist to remove iron from water and might be worth looking into if your water is extremely high in iron. 
- Use a dishwasher-safe rust remover for the stains themselves, but seek out a professional to ask how they got there in the first place.
- If the finish is chipping or flaking off the wire baskets in your dishwasher, try a paint-on sealant made just for dishwasher racks. Pull out the racks and check the bottoms, too. If the damage is severe or widespread (not just a few tines but all of them), see if you can replace the entire rack. Online stores sell a wide variety of appliance parts, so your replacement part may be very easy to find.
Replace all parts back into your dishwasher. Once the grate, filter, arms, and all the insides have been given their thorough cleaning and the smaller parts have had a chance to soak, place them back in as normal. Or proceed to the next section — if your dishwasher is really bad, you can take apart the bottom and really get down to business.