Couple of ways that Anonymouss didn't touch on. Hypnotic trance, and very young child who has not yet formed an opinion on what you trying to convince them of.
When we are very young, we soak up knowledge like a sponge. What is told to us initially forms the basis for that subject. Our mind just says (without words) Yes. That opinion given to us then becomes ours. We then usually go on to reinforce it by voluntarily giving attention to what affirms that opinion even more strongly. It comes as a shock - and generally against great inner resistance - to then change our minds on that subject.
That is why it is said, "Give me a child before the age of six and he/she is mine forever." In other words, the indoctrination will be so strong it will remain for life.
As for hypnotic trance. Well, that is another subject altogether. It, too, will convince - especially when one is actually UNDER the hypnotic spell. But there have been whole books written on this subject, so I'll say no more.