Tracy emailed in with the following tip:
We suffer from hard water even with a water softener — and we don’t always keep up with the salt like we should. I discovered that by just pouring about a cup or so of white vinegar into the bottom of my dishwasher it does a wonderful job of keeping hard water residue off my dishes — and white vinegar is so cheap! I don’t even need a drying agent. Just my cheap dishwashing powder soap and the white vinegar!