I very rarely straighten my hair. To avoid heat damage that can lead to breakage, I only straighten my hair 2 - 3 times a year. Prior to applying heat to my hair, there are a few things that I do to ensure that my hair remains healthy even during the straightening process. The steps to care for my hair prior to heat styling helps my hair to revert back to it's natural state.
1. Deep condition. I deep condition as part of my regular regimen and prior to applying heat to my hair. Deep conditioning helps to ensure that the moisture penetrates deeply into the hair shaft helping to prevent the hair to be dry and brittle.
2. Heat protestants. Using heat protestants that are silicon based coat the hair protecting the shaft from heat. It acts as a barrier to prevent damage while applying heat.
3. Low heat setting. My recommendation based on experience is to set the flat iron at no more than 350 degrees. The last thing you want to do is fry the hair. I remember my sister telling me about a time when she got her hair straightened years ago and you could not on hear her hair being fried, you could smell it. The damage was irreversible and she had to get her hair cut to get rid of the damage.
4. Limited passes. As seen in the video, I use the chase method. Using this technique allows me to only have to do one pass through to get my hair straight. More passes puts more heat on the hair which can lead to damage. I do no more than 1 - 2 passes.
Here is a detailed video of the process I use to straighten my hair.