From a Q&A with Anna Maxwell Martin:
You read history at Liverpool University ... I didn't do very much. I worked out with a very dear friend of mine that if we learned five facts about each thing, because we were both quite good at arguing, it would get us through any exam. You just needed five facts and a really good argument. We both got 2:1s.
This pretty much corresponds with what I used to advise my students in the run-up to the examination period. It was along the following lines. Emergency situation: you have done what you can on the exam paper, but you are still one answer light and can see no question you can readily tackle. So you pick the one about which you are least ignorant and take five minutes of your allotted time for that question just to think. Doesn't matter what it is, Mill on liberty, Weber on bureacracy, Marx on class, etc - write down half a dozen points you think you might know on the subject; anything, however small or seemingly insignificant. Then make an argument out of them. If you do this somehow, you're unlikely to fail; if averagely, you'll get a 2.2; and if well, you'll get better than that.
Of course, it's preferable to know enough not to face the exam emergency at all, but you need not to panic should it happen. And if you can't even scrape together those half dozen points? Ahhh, then all bets are off.