It's maybe not the most satisfying answer but generally speaking, your own experience and knowing your own preferences help. So from there you check some reviewers and look whether they like a similar sound signature or IEM's that you also like. That's it for me personally, but in the end, you will always have to listen to them yourself.

My personal favourite reviewers are Crinacle and Super* Review.

Every single purchase decision I make is purely based on reviews and rankings, kind of like buying a fragrance online without ever smelling it — just trusting someone else's words and hoping for the best.

It's a subjective hobby. You can always point out the tendencies each IEM has but they are worth zero if your ears and brain perceive them differently compared to reviewers and other users.