I like to first assess a students strengths and weaknesses by a use of a small set of questions, and their own opinion. I then use these to work with the student and undertsand their thought process and try to demonstrate a thought process useful to mathematics. I aim to make school too easy for them.
I use curriculum from the school of the student and design lessons based upon this.
Exam preparation is done by much smaller sets of questions and then a practice paper to again identify target areas.