Main tactics used by religion

Religions have formed (or evolved, if you pardon the pun) during the millenia. Some tactics used by religions have become very prevalent because they are so effective due to how human psychology works. Here are some of them.

Guilt

Many people do not fully realize this, but from all the tactics used by religions, including the ones listed in this post, guilt is possibly the most fundamental and effective one. It's even more fundamental than fear or intimidation.

The basic tactic is to make the person feel wrong about themselves. Things that you normally do are  wrong, harmful, and shameful. You are guilty, you are a bad person at a fundamental level, you are worthless. Most importantly, you must immediately correct these problems if you want to make amends and be a slightly better person.

Usually it's important to emphasize that no matter what you do, you can never get completely rid of the shame and bad things, not in this life, but at least you can make amends to be slightly better and to earn your better standing in the afterlife. In other words, it's not like you can just make amends, do some magic rituals and poof, you are a good person again. No, you can become slightly better, but never completely perfect. The sense of guilt must always be maintained, even if you try to do something about it.

Of course the solution to this enormous problem is, what else, the religion that's being sold via this guilt trip. You must accept the religion and fully submit to it, and you must spread it further, teaching it to others.

This tactic abuses the fact that humans are naturally gullible. We have evolved that way because it has been a survival advantage during the history of humanity. (If someone tells you that there's something wrong with what you are doing, that it's dangerous, in average it's more beneficial for your survival to believe it than to ignore it. Thus instinctive gullibility has been naturally selected into the human psyche.)

Fear

Of course the other extremely common tactic is eliciting fear and intimidation. If you don't do what the religion mandates, you will experience great suffering, either in this life or in the afterlife (or, in the case of some religions, in your next life.)

Christianity has taken this to its logical extreme: Indescribable endless torture, the worst possible pain and suffering you could ever imagine, up to eleven, for all eternity. The greatest possible punishment that the human mind can come up with.

And why not. If you can scare people into accepting your religion, then why not go all the way to the absolute extreme with it? Especially since so many people are ready to believe it, completely disregarding the logic of it. (It really is quite amazing how the exact same person could claim that a perfectly good, all-loving god who is incapable of evil could punish people with the worst possible torture that can be imagined for all eternity. This is almost Orwellian double-think.)

Demonization of the opposition

Demonization of the "enemy" has been a common tactic for all kind of warfare during the entirety of human history, be it physical warfare or just "warfare" at the ideological level. It consists of making the opponents to be depicted as extremely unpleasant, horrible, wicked and dangerous.

This tactic actually serves two roles. Firstly, it gives confidence to your own followers that they are in the right path and that "fighting" the opponents is a good thing. Secondly, to instill fear into your followers (in other words, if you ever leave the religion, you will become such a wicked and horrible monster as those, and you wouldn't want that, would you?)

Sometimes the "opponents" to demonize are people, usually people who follow a different religion or don't follow any religion at all. Sometimes the "opponent" is at an ideological level.

Science is a perfect example of the latter category. Many believers demonize science, especially certain branches of it, and make all kind of outlandish claims about it, such as it being a demonic plot, a world-wide conspiracy to overthrow religion, the biggest lie ever told, and of course extremely dangerous (for example that the theory of evolution causes this and that negative thing, such as racism or the holocaust.)