Organization is absolutely the key. Color coding folders is one easy way to always know which subject your grabbing. In addition, rather than label the folder tab, I staple a copy of whatever the document is on the outside of the file. That way when I'm scrolling through the file cabinet, I can see right away if that is the file I'm searching for. They seem like small things, but they save a lot of time for me during lesson preparation.
If you're asking about getting certified in different subjects, usually it requires different classes and coursework. When you accumulate the correct amount of required classes and pass the tests, you can apply for a certification to teach in that area.
If you are asking about organization, I think it's two fold, mental and physical. Mentally, it can be hard to keep straight what you've taught in various classes and what is coming up next. I write a lot of lists, organizing them by subject and class. Physically, I find that keeping organized files (both paper files and computer files) helps me a lot. I spend a lot of time organizing, making piles that I will use that day, and if I don't get to something (I always over-plan) then I bump it to the next day. But I always have work laid out for each day. Teaching involves a lot of paperwork, and I think that it's really important to have some method of organization so things don't slip through the cracks.
How do you teach many different subjects?
How to teach different subjects?
As a fourth grade teacher, I have to teach several subjects in a day's time in order to meet our state's requirements. It can get quite hectic at times, but it all works out in the end. All I can say is that the more organized I am, the better and smoother my day and year goes. For every hour a day I put in in the classroom there are 3-4 unseen hours after school, at home, at the library, and in teacher meetings. I usually teach each subject at the same time every day, but sometimes I like to mix things around just to keep the students interested and on their toes. I've also found if I highlight each thing I get accomplished every day it's easy to see what still needs to be covered another day. Many times I will explain a new concept in the 15-20 minutes I've set aside for a lesson, making sure all my students understand it. Then, I'll send them home with the deskwork to do as homework.
I teach multiple subjects and it is really a matter of organization. It is incredibly important to be as organized as possible.
If you are asking in regards to getting endorsed to teach different subjects then this is something you would need to discuss with a school counselor. It really depends on which courses you have already taken. Sometimes all you need is one additional class to get an endorsement but on the other hand you may need more. The more endorsements you have, the more marketable you are.