10 year Teacher. I started teaching in NYC, and now am teaching in Texas.
There is no such thing as a national certificate to teach. There is a national certificate but in all honesty it's a waste of money. If you stay in NY, (at least this was the rule ten years ago), you'll need a Masters. I'd recommend going ahead and getting your teaching certificate through a masters program than alt cert. as it is higher quality, better respected, and a lot of states you'll need it for tenure.
NY pays teachers well. Really well. But in the city, I'll be honest it's hard. I did not feel that I got backed up by the admins, anywhere.
Elsewhere, the pay is . . . . eh . . . . not the best, but you can augment it.
After ten years and with a masters, I make $55K. I do consulting work with the College Board in the summer, sub during the summer, Saturday school, and earn a stipened as dept. chair. All, in all, that brings in an extra $5000 a year. One secret, I have learned, as someone who has anxiety in new situations, is don't work Summer School, sub during summer school. In all the districts I've worked in, it is the same rate as the full time teachers, you typically can pick your own hours, and you will always be needed.
Experience is the best, so do volunteering. When I came down to Texas, it was 2008 as the financial crisis was hitting and only had one year of professional experience. However, I also had a year of student teaching and three years of volunteering. The thing that got me hired or to the final two (and I got a few job offers) was the years of volunteering beforehand.
When I am hiring a teacher here is what I look for:
1.) Are you quick on your feet? The biggest talent for a teacher is to wing it. Had an awesome lesson using technology? Too bad the electricity went out. Had a great classroom discussion organized around your favorite text, and you even edited it to make it easier? Turns out, none of the students read it or did it.
2.) Do you see yourself as an educator or as an expert on your subject? The former last longer. It's about educating the kids. The latetr do not. A teacher who tries to do Mr. Holland's Opus or Dead Poet's Society, typically will get burnt out, find your average teenager enjoys Facebook more than you, and will typically get in trouble with the admin. A great teacher could make Algebra or Calculus or Anglo-Saxon poetry interesting.
3.) Do you read in your subject? To contradict what I just said, one still needs to be caught up in the subject. I always ask applicants what's the last professional and casual book or journal he or she read. This not only tells me if one stays with the professional subject, but are you going to be interesting as a colleague.