Say I just ran out of self-raising flour. What can I add to plain flour to make the equivalent?
According to http://southernfood.about.com/cs/breads/ht/self_rise_flour.htm, you would add 1.5 teaspoons baking powder and 1/2 teaspoon salt to each cup of flour.
Salt is only added to US self-rising flour. In the UK, where it's called self-raising flour there is no salt added to the flour itself.