Regular trims, I know that sounds counter productive *but* getting rid of split ends every couple months prevents breakage so that it can grow long + thick.
Biotin as well as other hair skin and nail supplements are great because help to strengthen the hair and gives it the best possible chance of survival out in the elements
Lower the heat settings on your hot tools (250-300) and use a thermal protecting spray before styling. On damp hair I like to use the UNITE 7 Seconds leave-in and on dry hair before I curl I love the UNITE 7 Seconds Glossing spray.
Deep conditioning treatments will keep your hair nourished, strong and moisturized, I like to do them once a week (on Sundays, its my spa day). Some of my favorite deeply hydrating masks are the ENJOY hair mask and the DAVINES Minu treatment.
One last quick tip! Drink lots of water and stay hydrated because dehydration halts hair growth and we definitely don't want that.