The trick here is to make an objective decision. This includes whether you are determining on your own if someone is a godol, or even if you want to determine who is a maven on who is a godol so you will have someone from whom to take direction. A godol is someone whose Torah scholarship and righteousness are exceptional among the generation. Of course, he has to follow the derech of our previous Gedolim, the Mesorah of Klal Yisroel as well. That is pretty much unanimously the derech of the Chofetz Chaim, Rav Chaim Brisker, and their great contemporaries.
It does not include the following criteria:
(a) Who the Yated decides is a godol.
(b) Who the people who make “gedolim cards” decide who is a godol.
(c) Who has a lot of followers.
(d) Who is a popular and talented speaker.
(e) Who preaches policies that you agree with.
If you want to know if someone is a godol, think:
Is his scholarship level exceptional in the generation? Does his knowledge span all areas of Torah – shas poskim, halachah and hashkafa. And is his knowledge deep and sharp. Can he answer the difficult questions in Torah better than his contemporaries? Are his chidushim exceptionally sharp and sure? Can he decipher Torah difficulties in an exceptional manner? Then, what about his Tzidkus? Is he an exceptional Tzadik? If so, in what measurable way? If he wouldnt be a rosh yeshiva or a rav, but a yeshiva guy learning in the Lakewood Kollel, would people look at him as such a great Tzadik and Talmid Chacham as theny do now? Or is it just cuz of his position that people inflate his status? Does he violate the Torah? Does he follow a Rebbi of his? Does he have a “mesorah” going back to the previous generations whose derech he is following? Do other people of the above caliber hold he is a godol? All of us, whether we admit it or not, all decide on our own who is a godol, of what criteria we are going to use to determine that. We ALL have our criteria that we decided on our own to use (even if we decide that we cant know who is a godol, we decide who will will believe when they say it). The trick is to use proper criteria. It is also important for the person to be wise and sharp. It is definitely possible for a Godol to be uninformed, misinformed, or underinformed. The Satmar Rebbe ZT”L used to say that a Godol BaTorah can be naive as well. The most we can do is to try our best. More than that, Hashem does not require from us. The above criteria are the ones to use. The trick is not to have Hashem tell us we should have put more effort into the decision.