The exam itself is not that difficult overall. There are some questions that will stump you, like the one we had was a EAWR question out of nowhere, but after reading through the question again it was not as difficult as first thought.
Try to stay calm, take a drink of water with you. Eat before the exam, so your brain is functioning. Manage your time well. Read every question through twice, if not more and plan out your answers. I finished the exam in 1 hour and 30 minutes, but realized afterward I could of elaborated more in my answers to maximize on marking, but would of meant tipp-ex'ing a lot of what I wrote out. I had a couple of friends sitting the exam and they finished before me, so I rushed it through, just so I could go for a beer with them. Use all the time necessary, go back to a question you find difficult later, do not dwell on it, like I did.
For the formulas, remember to write every step, for an r1 + r2 on a ring for example, remember to divide by 4, etc. Write down the formula even if you cant remember how to do it.
Pay more attention to the questions with higher marks available. Remember your earth fault loop drawings, ring testing procedure, order of tests, testing with an emphasis on safety first.
You have probably already been told this by your lecturer, but it is all true. Be confident, stay calm, manage your nerves and time well. You will do fine.
Good luck
