How to learn to evaluate investment? (PE case study interview)

Hello guys!

Was hoping to get your help on this. As i am prepping for PE case study interview, I was trying to create a strategy of how to pass it. I have never made investment recommendations in my life. Although, I've read some case studies on investments and research reports on companies, but still I don't have a feeling how to make a GOOD investment. All decent companies seem to have good management teams, opportunitites to expand geographically, expect to grow inorganically, either strongly positioned in their mature market or address attractive underpenetrated, etc. I can see an obvious red flag - declining revenues, shrinking margins, very cyclical industry, customer concentration, etc., but beyond that don't really know how to bring value giving investment recommendations.

I would very much like to impress my interviewers with my performance on the case study, but would appreciate your help on this. I am keen to follow "practice makes perfect" approach, but for that i need some resources where i can try to make my own opinion on investment and then compare with the "right" answer.

What do you think would be most efficient way to prepare and to become good in differentiating good vs bad investments?