I’m interested in everyday applications like noticing bias in commercial media as well as word-of-mouth and social media. Are there any principles or methods you know of that you’d consider especially important?

I’m also interested in any recommendations for online training.

Edit: Wow! Since there are some great suggestions in the comments, I'd like to summarise them here:

• Primary sources and secondary sources (fefellama)
• Engagement (BeanBurrito)
• Under The Influence by Terry O'Reilly [podcast] (chocobean)
• Influence, marketing, motivation, bias, dark patterns, corruption, phrasing and choice of words (chocobean)
• Multiple sources. Verbalise your thought process / question yourself (hobofarmer)
• Advanced Placement English. Ethos, pathos, logos (Wisix)
• Learning how to hold and study concepts without internalizing them. Not becoming emotionally dependent on “being right”. (bet)
• Flaws in perception and processing. The Scout Mindset by Julia Galef: "the motivation to see things as they are, not as you wish they were" (Landhund)
• Fact checking, exercises such as mock trials (chizcurl)
• Not assuming that critical thinking transfers across domains (daywalker)
• Falsifiability, scientific psychology, psychological bias, cognition / emotion / behaviour (daywalker)
• 'Very Short Introductions' series by Oxford Press (daywalker)
• Many ways to conceptualise "critical thinking". Appreciating the humanity of other people. (mieum)
• Self reflection and acknowledgement of diversity (mieum)
• The Unpersuadables: Adventures with the Enemies of Science [book] (gaywallet)
• Being Wrong: Adventures on the Margin of Error [book] (boxer_dogs_dance)
• Be curious and ask questions (Markpelly)
• Empathy facilitates understanding and tempers reactivity (Aerrol)
• Nobel disease or Nobelitis (saturnV)