How can I keep my hair straight after using a hair straightener?

Use a straightening balm or spray before you do it. And also, use a heat protectant that helps with straightening your hair. Spray some hair spray on a brush then brush your hair out after you style it. Also, you could put a golf ball size of mousse in your hair when it is still damp, then blow dry. That will help keep it straighter. I do all of this and I have fairly curly hair, and my hair stays straight all day long.