If you misfired with the seasoning (and we all do that sometimes!) and your curry is saltier than you like, don't throw it out. There are a few different remedies you can try to remove some of that salty taste.
It is a good first attempt (if you have potatoes on hand), but the results are debated. Some people believe potatoes act similarly to a sponge and will absorb some of the salt when added to a dish. However, others disagree. If you want to give it a try, simply peel and cut a large potato in half and add it to your curry. You can either let it sit in the dish for 10 minutes, or cook the curry with the potato over very low heat for a few minutes. Just don't forget to remove the potato before serving.
Adding a small amount of sugar will help balance the salty flavor, but only will work when your curry is slightly too salty, not overly salty. If you are trying to counteract a heavily salted dish with sugar, you will end up making the curry too sweet and inedible.
Adding Yogurt or Coconut Milk
Since many Indian curry recipes include yogurt or coconut milk, it is not out of character to add some to the dish and will help balance out the saltiness. You only need about 2 to 3 tablespoons of yogurt, coconut milk or cream, and should cook over low heat for a few minutes to blend.
Adding More Onion-Tomato Paste
Most curries begin with a paste--or masala--made from grinding onion and tomato and then cooking it along with typical Indian spices. Making another batch of the onion and tomato paste (without any seasoning) and adding to the curry will help decrease the salty taste. Cook over very low heat for a few minutes and then taste and adjust seasoning if necessary.
Depending on the type of curry you've made, you can also add some canned tomato paste or chopped tomato.
Draining the Liquid
If your curry has a decent amount of liquid, you can strain the gravy and discard the liquid. Then place remaining gravy in a skillet, add new liquid (a little more than you would like in the finished dish) and cook at a low simmer until it is the right consistency. Taste for seasoning.
Boiling with Chapati Dough
If you happen to have some chapati dough on hand, add a few balls of kneaded dough to the curry and bring to a boil for 3 to 4 minutes. Turn off the heat and let sit for another 6 or 7 minutes and discard dough. The chapati dough should soak up some of the salt.
Converting or Doubling Your Recipe
If you've oversalted a vegetable curry, you can convert it into a gravy by blending it with cooked onion and tomato, plus a bit of water, and then cook it for 4 to 5 minutes. Check for seasoning and use as a gravy for your next curry.
Alternatively, you can make a whole new batch of the curry--but don't forget to eliminate the salt--and combine with the original curry. Or you can make a complimentary curry (for example, if your chicken curry is too salty make a vegetable curry and combine).