How should we use quotations in an exam?

You should close read each quotation, picking each one apart to show your ability for deep analysis. Do not just slot in as many quotations as you can to show you how well you have memorised them, but instead try to only use ones that have most impact on the point you are trying to express. Obviously, including only one or two quotations is going to look like you have not done a lot of work, but throwing in fifteen quotations that you do not do anything with will have little impact, and appear as if you are just trying to pad out the essay. I would say around ten quotations per essay is more than enough, but make sure that you are picking apart each one.