I agree with Eric about it the lesson not always focusing on teaching the students English. However, they should be in an English environment. At one of my locations I do arts + crafts or a special activity every lesson. Crafts generally keep the sts interested for a long time (sometimes up to 30 mins), and the sts will be immersed in a lot of incidental language (cut the paper etc).
I'm intending to keep the environment as exclusively English as possible. Basic instructions will be one of the main aims of the first weeks ie sit down, come here, colour the picture etc. Using their
creativity as a teaching tool is such a simple idea that it seems obvious, but I hadn't thought of it!