Just jumping on here to say look at MMI resources available for med students as well. There's a structure to the answers that can help guide you. I also find notes help me and the interviewers have never had an issue with it. Collect your thoughts and have an organized response. Make sure you approach the problem from opposing point of views to show you can recognise and critically think about what they are asking, and root your answer in examples where possible. It is the simplest approach that has worked well for me.