Once you have explained the grammar rule and make certain there are no doubts, I start getting doubts like "what if I forgot something" someting like things that are obvious to me but not to my students... so this book becomes a checking list of my teaching. Interferences from student's L1 come alive and you can deal with them explaining the difference between L1 and English.
All units come in questions starting with how or when which makes it easy to consult. Also exercises for further checking.
Thanks
Enza
English as a Foreign Language teacher