Get an Adjustable Flat Iron
Most professional flat irons are built to sustain heavy use and work as efficiently as possible, which means they are hotter by default. You on the other hand, need an iron which has adjustable temperature settings, so you don’t end up burning your locks the first time you use it.
While you are at it, also look for irons with ceramic plates, and choose a size that goes with the length of your hair (wide iron for long hair, thin iron for short).
Not a Wet Hair on Your Head
Remember this general rule – never, ever use a flat iron on wet hair. If you have ever sprayed water on a hot utensil or a heater, you should know what happens. Water evaporates very quickly on contact with a hot surface (accompanied by sizzling sounds), and when the same happens to your hair, they are left extremely dry and damaged.
Even if your iron claims that it works with wet hair, avoid it altogether. Instead, wash your hair the night before you need to straighten them, to make sure they are thoroughly dry before you use the iron on them.
If you want to prepare them rather quickly, use a blow dryer (on medium heat) to dry your hair first and make sure there is not a single wet hair on your head before you proceed.
There are several sprays available that protect hair from heat damage. Similarly, oil based products can also be found to serve as heat protectors against the flat iron. You simply rub a little on your palm and massage your hair with it to ensure a protective coating before you use the iron.
Iron Your Hair Gently
Even during the ironing process you need to be gentle and patient to avoid any damage to your hair. You might already know that you need to start straightening your hair from the bottom up.
Start with a thin lower section, holding it up with a comb and then moving the iron over it slowly and gently all the way down. You can make a pass or two, but avoid going over the same section again and again.
-Don’t get a flat iron that doesn’t have ceramic plates.
-Don't straighten your hair every day.
-Make sure you moisturize your hair plenty to make up for the heat treatment.
-Don’t use a lot of gels or hair styling products in combination with a flat iron.
-Even setting your blow dryer to very hot can damage your hair.