How can I straighten my hair without damaging it badly..?

I have curly hair, and I hate it. I used to straighten it pretty much every day, but I haven't straightened my hair even once in a few months, so my hair has grown a lot longer and is less damaged. I just bought one hair product today that I thought might help my hair not get as damaged from straightening. It's a spray in treatment for damaged and weak overworked hair. Would that help if I sprayed that in my hair before I straighten it? Also, does a good conditioner help? Thanks!