How to tell a good scholar from a bad one?

How to tell a good scholar from a bad one?

1. Pick one of his work that is published single authored. You can only tell one’s research taste and writing style from the single authored work. Even a work with two authors does not distinguish his contribution, regardless of whether he is the first author or not. There are too many cases where the first author contribute little to the actual work load and it is nearly impossible to tell them apart. If you insist on investigating that, you will have to recognize his writing style and research field from the single authored work and then carefully compare them with the paper that is co-authored. This is quite amount of work and it is only possible if you are fully proficient in this area.
2. Exclude those works that are part of  work when they are PhD students. Many people can’t produce good works after their graduation. This phenomenon is particularly significant for PhDs graduated from 2nd tier US universities(ranking from 11 to 30 on university ranking list such as ARWU. No offense. Just several samples fall into this interval). Within US college, they can get ideas from seminars and academic advice from really good academic guys, yet they are nothing after leaving the atmosphere. If you see someone’s only first tier paper contains this sentence-“Part of the work was done when xx was a PhD student in the University of xxx”, then he is highly skeptical to a lack of capability to do research alone. You should not take that piece of work into consideration when assessing his academic potential. Note that I am not saying that any work within the period of PhD student are not valuable. I am saying that you should NOT take that work as the ONLY argument when assessing his academic capacity. You need more of his works to confirm. If he has other works and those works match the same research taste, research field and writing style, that’s robust conclusion. It is highly suspicious otherwise.