Believability of Ideas
In order for ideas to take hold, they must first be believable. Eventually they can be believable merely because of their memetic power of altering reality according to that the idea states, but until then it has to be believable without it having power to change reality in any way, because all ideas begin with zero believers. This means that the ideas that take hold all have to be very, very close to reality (or at least the part of reality that people can perceive), in order to be believed: beliefs are anchored in reality. This in turn is responsible for the fact that the world has not seen extreme change through its millennia of history.
Various techniques exist to help make ideas more believable:
Ancientization: People ascribe old things with power, as a natural extension of believing that their parents and other more senior people have more power. Hence, by making the idea seem older than it is, one makes an idea more powerful.
Sacrifice: An example of this is mandating that believers pray twice daily. People believe that there must be a reason for doing something that one wouldn’t want to do, or for not doing something one would want to do, and if they see others do it out of respect for a belief, then it helps to convince them that that belief is real, how else would it be warranted? Likewise, if they themselves have to meet these requirements, then they are more readily convinced that the belief they are doing this for is real.
Esoterization: People ascribe power to things they do not understand, as a result of its sheer mystery. Hence, by couching a belief in esoterica one can make people be more ready to believe in that idea.
Value Implication: An example of this is charging far extra for a service than what one would expect for something similar, such as singing a ‘magical ‘song. People ascribe value to price, hence raising price raises its apparent value. And if that thing has not nearly as much value based on their own belief system, they become more accepting of the idea that some other idea gives it value, and that the other idea is true.
Rarity Implication: An example of this is only making a ritual available under particular situations such as a full moon. People believe something to be precious if it is rare, hence making something rarer makes it seem more precious, and thus increases its apparent value. At this point, see above.
Ancillary Rumors: People are more ready to believe ideas that are corroborated by other ideas - preferably ones not obviously being spread by the same people. Hence, the spreading of these alternate rumors that lightly corroborate with the primary idea, makes the primary idea more believable.