
Not Using Heat Protectant Spray: This goes for any heat styling tool, but if you’re not putting a heat protectant spray on your hair before using your flat iron, it’s like asking for damage. On clean, damp hair, spray in a heat protectant to keep your hair from the harm that hot tools can cause.
Ironing straight down: Getting as close to your root as possible, flat iron each section of hair, but pull the hair up instead of going straight down. This will give you a boost of volume at the crown, so you’ll have straight hair with body instead of your hair falling flat.
How you adjust the temperature: The natural thought may be, “If heat damages my hair, I’ll keep my flat iron on the lowest heat setting possible!” Counter intuitive as it may seem, a medium to higher temperature — lower if your hair is fine, higher if your hair is thick — is better, because on a low heat setting, you’ll be going over your hair multiple times to smooth it out. A higher temperature means a better chance that a single pass can do the trick.
Not using a brush: With each section you straighten, brush out the hair first to get any kinks out of the way before you hit it with heat. Doing this will make the straightening go much more smoothly, and can reduce the need to go back over certain areas multiple times.
Not letting your hair cool down: While heat styles hair, cool air works to set it. Allow your hair to cool once you’ve flat ironed it so that it holds the straight style, instead of immediately putting it into a ponytail or a hair clip.

Ironing while your hair is damp: Under no circumstances whatsoever should you flat iron your hair while it’s damp. If you’re in a rush, hit hair with a blow dryer before using the flat iron. When you can, allow your hair to air dry so that you aren’t putting double the amount of heat on strands.
Neglecting to clean the iron: Between using heat protectant spray and any other styling products that may be in your hair, build up can — and will — happen on your flat iron, which can cause it to snag your hair. For a smooth, clean style, make sure you’re cleaning your flat iron regularly