The book also has an interesting statistic (IIRC in the chapter about cutting in line for a photo-copier) of people that were first interviewed whether they thought they'd fall for (an abstract explanation of) the trick, who were then (unknowingly, as a set up psych experiment) exposed to a real-life situation playing that exact trick.
The percentage of people that were confident they wouldn't fall for it, but then in a real-life situation did, was surprisingly high. I don't remember how high exactly (maybe someone who's also read it can fill me in here?), but it was enough to seriously question my own confidence (in not being affected by certain human flaws), and make an effort in being extra conscious about that even when I rationalize myself to be immune (which seemed to be a common theme in defence tactics).
Not so much even to avoid being suckered or allowing people to cut in line, but especially after the chapter on Kitty Genovese type tragedies (aka "the bystander effect"). That chapter btw has a bunch of more specific defence tactics such as singling out people and talking to them directly instead of to a group (even if you feel you're not qualified or whatever to be the hero, you can always say "You, sir, in the blue jacket, you seem strong enough, please jump in the water and save that person!", which may feel cowardly but if it helps breaking the "bystander spell" and someone's life being saved, what the fuck does it matter?)