Know your texts inside and out! When you write an essay, make sure your argument is sustained all the way through and has strong evidence to back it up
If your argument is strong, then usually its enough to get away with. But if you're scared add a few sophisticated words here and there
Also, start with a plan! Often, your thesis will be the first thing that pops into your head, so use that and develop all your ideas for that and go for it. It also takes a lot of practise to be able to do that so familiarise yourself with different questions before you head into the exam :3