I spent the day before mine answering other people's questions on here haha.
I certainly wouldn't be doing any practice exams then - a bit of light study would be fine eg. reading over notes/drawing mindmaps/whatever else works for you. Doing a practice exam the day before is more likely to just make you stressed than actually help though.
One of the most important things will be making sure that you're calm and focused on the morning of your exam, that will help you more than any last minute cramming. Doing things you find relaxing and eating properly like Bri suggested will help with that. Remember to also drink plenty of water, get a good nights sleep, and make sure you've set an alarm/have everything organised/be prepared to leave a bit earlier than normal so that you have plenty of time and don't get stressed in the morning.