This isn’t going to be an explanation of how to identify and separate good ideas from bad ones because I don’t know. It’s more of an exploration of the problem of not always knowing the difference and how to get better at it.
First, sometimes it’s easy. (Almost) no one needs to exercise a great deal of critical thinking to know that Billy Mays’ screaming about a sham wow is dumb.
Second, sometimes it’s hard. When your math prof gets something wrong nobody points it out. Anyone who caught the error often continues to think the prof is correct and search for his or her own error.
Third, circumstances may make a person more vulnerable to a bad idea. If I’m hungry, tired, stressed, emotionally distraught, or all of the above I’m more likely to just nod my head and go along with whatever.
Fourth, there is an element of groupthink at play. If a bad idea catches on and reaches critical mass you’re more likely to doubt your own disagreement and accept the false logic of it.
So what to do? Determining the source of the idea is probably a good start. When my wife tells me that eating raw meat is going to raise our kids IQ because she read about it in a mom group on Facebook I know that I need to carefully scrutinize that suggestion.
Related to considering the source is finding the real source. When a publication reports on a “study” it invariably gets the science wrong. Moreover, the study itself could be poorly designed. There is a reasonable chance that the reporting contains an inaccurate statement of a conclusion based on a hypothesis that the study couldn’t even properly test. Filter that through word of mouth a few times and you’ll see just how fucked up your information is.
Developing a set of principles (eg. Seeking truth) is probably a good way to sort ideas as well, but I don’t think I’m qualified to write about that. I mean other than the principle of presume bullshit until proven otherwise.