How can I make my hair grow long faster and more healthy?

I have never had long hair. The longest I ever got to long hair was like a lil longer than shoulder length hair and I'm finally trying to grow it out. I usually cut it when it gets to about shoulder length. My hair is now like below my neck. I have fine curlyish hair. What tips are they're to make the process faster. What can deter it from growing. I straighten my hair a lot. Will that hurt it? Is there anything I can use?