Formal guides and cultural training have their place, but experience is where culture actually gets learned. A guidebook can tell you the rules; only living among locals teaches you the exceptions, the tone, the timing, and the thousand micro-signals no author can write down. Sharing meals, shopping at neighborhood markets, attending festivals, making local friends, and yes, making small public mistakes and being corrected, these compress years of theoretical learning into months.
That said, dismissing formal preparation entirely is a mistake. Guides are excellent for the high-stakes basics: serious taboos, religious sensitivities, business protocol, and legal differences, exactly the areas where learning by trial and error is costly. The smart sequence is preparation first for the dangerous mistakes, then immersion for everything else.
The multiplier on all of it is reflection: people who ask locals why things are done a certain way, and adjust after each awkward moment, integrate far faster than those who simply let the years pass.