According to Jigme Lingpa, there are four different kinds of gurus [i.e. spiritual teachers] to be avoided. First, avoid a guru who is like a wooden millstone, constantly talking about his family, lineage, history and monastery [or organisation]. A wooden millstone is very noisy but doesn’t do the job [of teaching the actual Dharma].
Second, avoid a guru who acts like a frog in a well. These lamas, even though they have no enlightened qualities, must have had a shred of [‘good’] karma to be reborn as powerful, influential, good-looking people from good families. Now they think they are special. Of course, their disciples also are made to think that way, and therefore they also praise the lamas [or laypersons], making a complete circle of praise to reinforce something that is completely untrue. When these gurus see other masters who have much better [spiritual] qualities, they stubbornly think, ‘I am better than he is.’ They are like a proud frog that lives in a well, boasting about its abode to a frog that lives in a lake he cannot even fathom.
Third, avoid a mad guide. Some gurus have a sliver of knowledge of the Dharma and may have met good gurus [themselves]. They may even have a bit of supernatural power. With these they make people believe they are much more capable than they are. They display a kind of madman quality, flaunting that they transcended mundane worries and cares. They don’t care about benefiting sentient beings. They don’t care that their activities may end up harming or disillusioning someone. This is what happens when you have a mad guide leading you.
Fourth, avoid the blind captain who insists on guiding you. The guru is on the path to enlightenment, same as you, but he or she must have more realised qualities of knowledge and realisation. If the student is on the path of accumulation, it makes sense if the guru is on the path of application – otherwise the guru will not know how to advance the student.