To help you with word formation in the Cambridge: First exam
Here is an overview of part 3 of the Reading & Use of English paper for the 2015 exam from the famous Flo-Joe website’s YouTube videos:
The following videos from Crown Academy of English will look at affixes in more detail
ADDITIONAL STUDY MATERIAL
The following slideshare materials can help you know when to use a certain affix, as well as the spelling changes sometimes needed.