Finally got my SC-900 done after about three weeks of studying and honestly I'm still a little surprised I passed on the first try. I work in IT support so I had some baseline knowledge about Microsoft products, but the security and compliance side was pretty new to me. I was aiming for 750+ and ended up with an 812, so I'm happy with that.
The thing that helped most was doing a ton of SC 900 practice test questions — like, way more than I thought I'd need. Reading the study guide gave me the concepts, but actually working through questions under timed conditions is what made them stick. I kept getting tripped up on the differences between Azure AD Identity Protection and Conditional Access until I just drilled questions on that specific area.
For anyone starting out, the exam covers three main pillars: security, compliance, and identity. Don't underestimate the compliance section — I almost did and it nearly cost me. Happy to answer questions if anyone's prepping right now.