My first suggestion is not to prepare for your exams alone. Prepare for your exams with some of your colleagues, but make sure each of you reflects on your own progress toward readiness independently; the role of you and your colleagues is to provide feedback for each other.
My next suggestion is to identify areas of concern and focus your efforts on these areas. Which topics are the most challenging for you, and which topics do you actually have evidence you understand (do not rely on "oh I remember how to do this, try practice problems and verify you can produce the same answers as your source of the problems").
You should also regularly quiz yourself on the topics. There is evidence to suggest that our brains memory emphasizes information which is regularly retrieved, which means that just taking a quiz helps you remember that information, since you essentially force your brain to recall it.
Next, you should ideally attempt non-standard problems in the domain of mathematics you are attempting. A recent randomized-control study suggests that if you follow a sequence of steps someone else provides in order to solve a problem, you are less successful at remember your attempts for later than if you just struggle with problems (presumably collaboration is helpful here) even if you do not get the answer to the problem. A non-standard problem without a known solution that lies within the domain of mathematics you are studying should help simulate this effect.
Find examples of work you did unsuccessfully in the past (or ideally, find a collection of such examples with you and your colleagues) and take the time to reflect on what worked in what you did, and what did not work.
Construct a 1 page summary of everything you learned in that content area, even if you do not get to use it during your exam. This summary should be clear and easy to read (don't use 2 point font!). Doing this will help you focus on the essential elements you need to understand for this unit, and creating it will help you recall those elements later.
Make sure in the days leading up to your exam that you relax. If you have taken the other suggestion from this post and spread our your preparation over the weeks in advance of your assessment, you will not need the last day to cram. You should take a break, get some rest, and be well hydrated (Hopefully this is obvious, but don't drink or do drugs during this day, both will negatively affect your performance) before your exam.