What's the best way to provide feedback on IH posts?

I've been a bit out of the loop here for a bit and as I'm looking to get back into helping other IndieHackers out I see a bunch of posts about people looking for feedback. I would love to help out but sometimes I don't know if my feedback is just my personal preferences or valuable critiques. This isn't me trying to come up with any side-project from it, but actually curious what is the best way to help others. I feel like giving good feedback can help me learn more and grow as a person as well. The design for X product may not be my personal favorite but it could fit the situation or target market, right?

Does anyone follow a set of steps or guidelines when looking at other products to provide feedback? Or is it personal anecdotes and experiences that could help push a product in one direction or another? Or any other system?

Or alternatively, if you have posted a product looking for feedback, what kind of feedback are you looking for?