Be careful....
CAP804
CAP393
Standards Document 10
...are UK specific. If you're doing your FI certificate elsewhere these will not be relevant.
The AIP for the country you want to do the training / teaching in is always worth a read - that should show any differences with ICAO standards as well. Any Statutory instruments that cover 'national' licences, again for the country your training in.
More generic, PART-ORA and PART-ARA cover the organisational and administrative parts - always good as background reading.
"Instructional Techniques for the Flight Instructor " from Ontrack is a good document
As a general guide re-read your PPL notes or The Air Pilot Manual Series (Trevor Thoms as was).