Realistic Questions Challenge

So, I thought I'd take a shot at the realistic challenges. I wasn't quite sure what to do on challenge 1, so I checked the articles and found a hint that pushed me in the right direction. After all, I figured, what's the harm? It's just the first challenge, I won't need to get hints on the next challenges. So then I went to challenge 2, where I didn't know what to do. Then I tried challenge 3, and I didn't know what to do.

So my question is, what's a good mindset for the realistic challenges? How do you know where to look? I imagine that, to an extent, you just need to look around, try things, look for hints of vulnerabilities. But … how do you know where to look?