I have been teaching 6-8 year-olds for a couple of years. Here are some tips that work for me:
1) structure. Start each lesson the same way (no book required). Greet the student, wait for proper reply, do a few familiar songs or routines before starting something new
2) use flash cards. Ideas on how to work with flash cards can be found at
ESL-Kids - Flashcards, Worksheets, Games and Songs
3) bring a cuddly toy. I usually use "George the curious monkey" and pretend that he only speaks English. So to introduce new language patterns or vocabulary, I model the dialogues with George. Also works when kids are sad or reluctant to speak as he is very cuddly (and very nosy). The kids love him!
Hope some of this works for you. Let me know. Good Luck