I have referred to different posts on this forum, summarized them to find what type of questions may come. That gave me enough information. Accordingly, I then bought different verbal reasoning books (CGP, Letts, FPTP, Bonds, S&S etc) to confirm my understanding. Some publishers have specific CEM type questions (e.g. CGP, Letts and Bond) and some have good question bank that will help your DD or DS to have a good understanding of English vocab that will help a lot (e.g. S&S Comprehensions, English skill books, First Aid English etc.).
I am going through all books myself now before giving to my DD who will sit CEM 2017 exam for 2018 entry.
One of the books that provides different techniques on CEM verbal is: CGP 11+ Verbal Reasoning Study guide (Amazon Link: https://www.amazon.co.uk/Verbal-Reasoni ... study+book