Student from another instructor

Folder
First thing that I'm going to look at in their folder is what lessons that they have completed.  This will at least give you an general idea of what they know and what the instructor has covered.  I would want to look at what ever notes that anyone may have put in the folder or on the specific lessons.  This would help me get more of an idea of what areas they were strong in or week in.  It would also be good to look at comments on any previous stage check they may have taken.

Previous instructor
I would want to talk to the previous instructor to get more information and clarify information from the folder that I had just looked at.  I would want to know what they had covered and not covered.  I would also want to know what they thought the student strengths and weaknesses are.  ask about the student personality.  What type of teaching technique may be best for them.  And also if there is anything else usefull they could tell me.

Ask the student
I would want to start by getting to know the student.  Asking them their personality and what their interest are.  Then I would ask them similar question to what I had asked their previous instructor and read in their file.  Would want to judge what they think they have covered vs what it is said in their file.  Would want to see if they knew what their weaknesses and strengths are.

Ground Knowledge
I would give them some ground briefings and assignments to asses where they are.  I would also ask them some questions. This should be able to provide me with an idea of what level they are on with their ground knowledge.