Adding too much salt to a dish is one of the easiest ways to ruin a recipe, but there's no need to throw away the dish immediately. You can unsalting, or desalting, the food to save a dish that would otherwise be inedible. The process is different depending on the dish you're preparing, but the basic principle of dilution will help save your dish. Adding more of the base ingredient will help overpower the taste of salt.
Add a little bit of extra water to soups and some sauces. This will help dilute the salt content of your dish. Taste the dish to see if it helps, but be careful, adding too much water can dilute the taste of your dish too much and render it tasteless. Add the water in 1/4 cup increments.
Place over-salted meat in a bowl with heated water and stir. The meat should be completely submerged in water. Let the bowl sit for a couple of minutes. Stir the mixture again and sieve out the contents. Repeat this process again if necessary and then reheat or cook the meat. Doing so will also wash away marinades.
Add more oil or vinegar to dressings and some garnishes. This will help balance the salt content of your dish.
Include a pinch of sugar. This will work in a wide array of dishes, but you'll need to be careful. Sugar can easily overpower the taste of your dish just as much as the salt.
Make a bed of rice if you're preparing a meat or vegetable dish. Rice provides a neutral flavor that will help unsalt your dish. This will also help partially neutralize overly spicy dishes.