1. Use alot of colour- highlighters, pens, pencils.. anything that you can do to highlight important information like equations, quotes..etc. Using colour is a good way for me to remember things, I will highlight information..then write down what I can remember and see if I got it right. If highlighting is impossible (like because its a library book) then write things down in sections, separate with colour make it something you want to read.
2. Treat yourself- You know all that loose change you have stocked up somewhere? It probably adds up to more than you think. So add it up, find something you want to buy and when your exams are over buy it as a treat for yourself... Well maybe don't give £40 in change to a shop, I don't think they will appreciate that too much..
3. Snacks- I'm a big fan of snacking, doesn't always have to be healthy!! fizzy strawberry laces are a big favourite for me.
4. One big thing is rest. Getting sleep, however difficult, is important. It'll help you feel more relaxed and you won't worry about sleeping through an exam.
I hope this has helped a little, even if it meant you were reading this while having a break from revision, good luck to everyone and hope you all stay as relaxed as possible :)