Critical thinking is a very simple process (and you will never find a step-by-step manual. Even though some books claim that like the bible and every WT literature), basically:
- Scientific method.
- Logic (in a nutshell: two true statements can't contradict one each other).
- Occam's razor.
- Fallacy detection (see some list of fallacies).
- Reality check.
If your worldview needs some flaw in evidence, internal logic, simple explanation and fallacies, you can be sure (99.9999%) you are being fooled.
And when this happen sooner or later your worldview will be crushed by the supreme judge of all worldviews: the reality.
Reality destroy every flawed worldview, like "1914 generation that will not pass away" and "communication with dead people", for instance.