By all means, always, always take out a pen and some paper during case study questions, unless the interviewer specifies not to. I have a very basic questions. I'm not sure what personal etiquette is, but I would assume that you should unbutton all suit button while seated. It presents a cleaner image than having 1 buttoned and the blazer puffing out while seated. David A. Three different references from three different companies are best.
Recruiters look for a variety of sources for feedback.
Use past supervisors, but provide accurate contact info if they are no longer with the same company.