Hi there,
I scored 4th quartile and it was my first time round. I studied for 1 or 2 hours the night before to help familiarize myself with the format, and also looked at some practice questions that they provide on their site. There are also some really good questions on reddit and some other sites if you google "practice casper questions". Youtube is also a good source, since they explain their reasoning after, and you can compare answers. It's best not to over-study just because you can psyche yourself out and you can often begin rambling or going off tangent once the exam begins.
Another tip is to practice your typing speed. I find this is really crucial because it allows you to really build on your reasoning, rather than just providing an answer or solution. I had friends who had great responses but simply couldn't type it all down with the tight time restraint. I didn't use bullet points, and tried my best to organize my thoughts by solution first, exploring other possible answers/solutions, and then explaining my main idea. Find free typing exams and practice when you can. You ideally want to get the point where you don't have to look at the keyboard. That way, you can think and type at the same time.
Really remember what they're testing, and incorporate that into your answer. For example, on Acuity Insights, they state that they test for collaboration, teamwork, communication, empathy, ethics, resilience etc. remember these and take a few core principles that you can really build on. I like to listen or read the question, understand the issue and ask myself what are the principles that can help resolve or de-escalate the situation. Writing on a page about the problem, whose involved and the principles helped me a lot in case I forgot while listening or reading the question. From there, you don't waste time formulating your answer from out of nowhere and it becomes easier to control your flow of thought. Try not to ramble. Waste no time with why and why not and move onto the next principle or strategy. With the video questions, I found that testing yourself with questions didn't actually help me much before the exam, rather than that, being able to remind myself to slow down, not use too many filler words like 'um', 'like' or 'uh' was much more helpful.
Finally, always being aware that you're testing as a medical professional or a career path that will often encounter high intensity situations is always important. Some of the scenarios on the exam would cause anyone to be irritated, and it's okay to express that you don't think it's fair or right to the adjudicator. They aren't looking for robots with a perfect response, but rather someone who can maintain empathy and accept their emotions to think logically under pressure without offending others or escalating a situation. Stating your true thoughts isn't an issue, and I know some people will say to fake a response full well knowing they wouldn't approach it that way in real life, but do your best to be authentic in the situation. What would you do? is that a good idea? what are some other ways that would be better? what is the best course of action at this time?. All good questions to ask yourself during each scenario. Try your best! It's always okay if they stop you while you're in the middle of writing. It's under a time restraint after all, and so knowing this and preparing for it can save your mental health and beating yourself up under pressure. After all, it's about the quality of what's already written rather than the quantity of what could've been.
I hope this helps!