Never fear! This is easy, peasy, lemon squeasy.
1. Empty the dishwasher and remove the racks. This makes it easier to get to everything.
2. Inspect the twirly arms. They should rotate freely.
3. Then check the holes in the twirly arms. This is actually the most important thing. Those little holes are actually the cleaning power of your dishwasher. The holes need to be clear so that the water can squirt out at high pressure. That is what gets the food off of the dishes.
I was almost sad to find that mine were clean. I found some super gross pictures on the internet of gunk that people found in those holes. If yours are full of gunk, simply use tweezers to carefully remove it. (and snap a picture and send it to me?)
4. Inspect the bottom of your dishwasher. I found a bobby pin in the drain. Can anyone explain why a bobby pin is in my dishwasher??? I can't think that the Dish Fairy lost it in there. After all, she has perfect hair. It's indestructible even.
5. Check the seal area on the dishwasher. This area does not get water on it during the cleaning cycle, so it could be pretty dirty. It had never even occurred to me to look there. Mine is pretty nasty.
This is in fact the same nut or bolt thing. Just a different camera angle.
6. Finally, reinstall the racks. Then fill a coffee cup full of white vinegar and put it on the top rack of the dishwasher and run a cycle on your normal setting.
Now, I'm realistic and I'm not going to go through all these steps very often, BUT I will run a load of vinegar every once in awhile.