Hay Nati, I didn't feel like writing a private message, lol.
I also teach in for language schools. As per my private lessons, they're really easy. You can find everything on the interent theses days. So you can google "ESL Past Simple" for example and a whole bunch of stuff will pop up.
The first "lesson" I try to get to know them and see what they need exactly. Try to get them to talk in different tenses to see what they are missing and ask them if they feel they need anything specifically.
I also have a good vocabulary book. If you know that a student is lacking in a particular area i just give them a handout and go over the explanation with them and do the exercises and try to work it into conversation.
There's a website called "One Stop English" and this website provides a free news article (in beginner, intermediate and advanced levels) with exercises. So you can read, converse and look at vocab, etc.
I think you'll find that students will usually tell you exactly what they need and that usually makes it very easy.
Does your school provide you with books?
