Most Helpful Guy
DON'T use a flat iron. It is horrible and tortures your hair. Stick with a blow drier and diligence :). If your hair isn't straight after a blow-dry leave it! Why would you want to have straight but suffering hair?
Your hair might be frizzy because of the heat damage. Additionally you can get deep conditioners for your hair (these are safe to leave in for 30 minutes or so) that really make it healthy and get rid of the frizz. Make sure you get deep conditioner though because leaving regular conditioner in your hair for longer than 5 minutes could actually damage it. Also don't use deep conditioners after dyeing your hair wait at least a week or you lose the color.
I use loreal on conditioners/shampoo and some japanese brand deep conditioner that I can't type. My hair is lovely though. Oh how vain I am.