If I became a teacher, what kind of teaching advice could you give me?

I heard on many occasions that in several years the US will need millions of more teachers (I’m not sure about any exact number though). If this is even remotely true that there is such a need, I’ve been considering getting my single-subject teaching credential; I’m in the process of earning my BA in English, the subject I would teach.

I’m also interested in this career path because I personally had a bad experience in high school. Half of my teachers couldn’t teach well, but the one’s that could were people I truly connected with and really learned from. I’m aware that teaching could become a job which could wear me out, but in the past few years of college I’ve noticed that I really enjoy helping fellow students see the bigger picture of their studies, especially students that have a really hard time grasping new ideas.

What are your opinions of this need for new teacher/better teaching? Is there any teaching advice you would have to someone who was just about to enter this field?

Also, do you think it would be wise to teach at a public school – or are there better school systems out there?