A few thoughts:
The stuff you own.
See how much you can secrete in the attics and spare rooms of parents and friends. However, be ruthless first. Is it really worth asking a friend to store that battered old frying pan? Wouldn't it be better to makes a fresh start when you come back, initially with something from Poundland?
If you try to sell your furniture, you'll find you get far less for it than you expect. On the other hand, it's a comforting thought to know that you'll have an idea of the price you'll have to pay for second-hand furniture when you get back - rather less than you expect.
The stuff you take
When you know where you are going, see if your future employer will put you in touch with some teachers there who can give you tips on what you must bring - and what you needn't bother to bring. Search the internet - many countries and some large cities have expat sites where you can find out all sorts of useful things. Find out the price of clothing. In some countries you can buy several outfits for the price of transporting one suitcase in the hold.
Think twice about books - they are heavy to carry. For your personal reading, invest in a kindle. Your school should have some sort of library of EFL books, though you might like to take your own treasured copy of Murphy or Swan, or whoever you rely on in your course. Do find room for the lesson plans you used on the course - they may come in handy in your early days.
Why do you need a printer? Your school should have one you can use. Toiletries? Unless you are working in the back of beyond, you should be able to find most things you need these days in the place you are going to.
Every time you put something in your 'to pack' corner, ask yourself if it is really essential that you carry it several hundred/thousand miles. And remember - if it's important enough to take, it will presumably be important enough to bring back. Take too much, and you will be unable to bring anything back from the country you are going to.
Now some advice that slightly contradicts what I have just written. Things like needles and thread, safety pins, tin-openers and tools (screwdrivers, scissors,etc) are of course obtainable in the country you are going to, but you might well find that you need them in the first couple of days of arriving - before you have had time to find out where to buy them. Consider buying a (fake) Swiss army knife and/or Leatherman-type multi-tool. - and one of those converter thingies so that you can plug in your laptop and the microwave that you couldn't resist taking.
Others may have other ideas. Start a new thread when you know where you are going, and you may get some replies from people who already work there.