I change the organization of my class to keep the students attention while I do my job and I want them to be happy during the class.
I know that varying the interaction between students helps to keep them motivated but I have to teach English every hour in different classes. Most of the time I can't move chairs or tables. I try to combine individual work with work in pairs. When they work with a partner, I try to put together two students with different level and that way they can help each other to improve their English while I go around the class helping all the pairs.
Students like activities that require completing a chart moving around the class and asking questions to their classmates. Even if they're 27 students in the class, there isn't too much noise.
Games that require role-playing between the students are activities that help them get more into the concepts of the lesson.
Going to the playground is a possibility that I use when I make groups and do some fun activities.