As your question is not specific, I cannot give a specific answer. My wife says: iron them damp with a warm (not hot) iron, and hang them as soon as possible. As regards net curtains, do not iron them, but hang them whilst they are still damp from washing. But it all depends on the material.
Haven't ironed anything in over 10 years. Take stuff out of the washing machine, shake thoroughly, gently pull into shape and put on a hanger to dry. That's it.