I love subbing as well! The flexibility is wonderful, and I've learned a lot about teaching methods, which helps when my own DS has homework questions.
It took a couple of weeks to get those first calls when I was new, but it does build up. I started mid-way through the 07-08 school year, and by the middle of last year I was already averaging 4 calls a week. (I also do 2 districts, with multiple buildings.) Around here, you kind of move up a list the longer you've been subbing.
Don't worry too much about lesson plans - they're usually required to have to something for emergencies, and quite often actually know they are going to be out and leave detailed sub plans. It's always good to have a few tricks though, in case something doesn't last as long as the teacher thought it would. - Kids always like games if you need to fill a little time:
for math - Around the World - One student stands by the next desk in the row (so two students compete per question.) You ask a problem at whatever level they're working (addition, multiplication, whatever) and the one to answer first moves on to the next desk, and so forth. The idea is to get all the way around the classroom and back to your own desk.
for spelling - Sparkle - Students stand in a circle, and one is designated to start. You give a spelling word, and that child says the first letter, next child says the second letter, etc. After the last letter, the next student repeats the word, and the next says "sparkle", and is out. If you miss a letter, or fail to recognize the end of the word, you are also out and must return to your desk. Last student standing wins.
for any subject - War (like the card game, but change the name if you feel you need to) - Divide the class into teams, who stand in parallel lines. Ask questions, as in Around the World, of the front two students. The one who gets it correct first moves to the back of his or her line. The idea is to get your whole team to win a question, and your "captain" back to the front.
As to teaching out of your speciality area, you'll be fine with regular classes in the elementary grades. All the information you need is usually there in the book. For specials (art, music...) or middle school, you should be told the subject when you get the call, and can decide if you're comfortable. - But really, the teachers are told not to expect a specialist in their subject, and tend to leave sub plans anyone can follow. So I actually run into the opposite problem when I do hit my subject (math.) - They just leave worksheets because they are unsure who they'll get, when I could really do so much more for them. The only thing I personally tend to avoid is music.
Good luck, and have a great year!
