First, I think this can be said for any field: the textbooks don't tell you what you really need to know, because what you really need to know is a state of mind that you can only arrive at on your own.

And there are many scientists who do in fact spend time puzzling over how to distinguish good hypotheses from bad. Some don't, and they spend their days predicting what the future will be like in 2050. But they need not concern us, because they are just examples of people who are bad at what they do.

There is this famous essay: http://www.quackwatch.com/01QuackeryRelatedTopics/signs.html

And also this one: http://wwwcdf.pd.infn.it/~loreti/science.html