Language Assistant by Clare Lavery
On the British Council website, there is an excellent resource book for native English-speaking language assistants. The manual can be downloaded (free!) in PDF format.
This manual provides clear, concise explanations of basic ELT methodology for assistants who may not have much initial training. It also gives examples of how assistants can collaborate more effectively with local teachers in the classroom. This book would be useful as a textbook-manual for newly-arrived assistants, as well as a starting point for discussion between assistants and local teachers when planning team-teaching activities for the classroom.