This isn't in itself culty -- but it is the cult attractor that's causing your problems, in a roundabout way.

When we hear people talking about some proposition, we normally either throw it out entirely or tentatively integrate its consequences into our thinking, modulo considerations of status and so forth. Normally higher-impact propositions assume higher priority in our thinking: a perfect stranger shouting "My God, the office is on fire!" takes higher priority than a friend telling you your shoelace is untied.

The memetic ecosystem we live in does contain cults and similar predators, though, which are best recognized (almost defined) by wildly overvaluing their core values. That translates into communication as what might be described as great vehemence. Very high-impact propositions, therefore, carry strong if unconscious connotations of MIND-KILLER STAY AWAY STAY AWAY; after some inflection point, they'll start getting discarded often enough that the priority effects are overtaken.

This isn't just theory. We're all constantly bombarded with exhortations to save the world, and for people who are not domain experts or highly skilled rational thinkers there's no good way to differentiate reliable world-saving imperatives from unreliable ones. The obvious priority-preserving move is to make sympathetic noises and refuse to update -- which indeed turns out to be the polite, socially expected response. If you don't want that to happen, expressing your views in terms of saving the world is strongly contraindicated.

From what I've gathered (can't find the link) Eliezer's attempt to answer this question eventually resulted in him deciding to focus on creating rationalists, rather than getting individual people to support particular causes he believed in

More things to say, which I'll say later, because I have to go to bed. One question though: which Alicorn post are you referring to?

My two cents about influencing people to work on a cause:

• Usually, the most effective way to do so is to engage their emotions. Any discussion of existential risk implicitly engages people's fear, for example. That's a bit problematic in this case, since they'd be working within a community that tends to disparage signaling emotionalism. My guess is a happy medium is to engage people's emotions while signaling alliance to rationality. EY's "rationality dojo" posts are a good example of this, IMHO.

• Causes may be general, but actions are specific. If I want to encourage action, therefore, I ought to be as specific as possible about what I want people to do. Often a useful combination is to raise a general problem and suggest a specific action people can perform to avoid it. It helps if the two are actually related in some way, though it's disappointingly unnecessary in many cases.

• Convincing groups is even more effective than convincing individuals, since groups have a way of mutually reinforcing one another. Of course, groups also have a lot more inertia to overcome, for the same reasons.

• You don't "only need to convince them once." Actual persistent behavior change is not usually a fire-and-forget thing; it's the result of continual effort. One reason so few people manage it is because we aren't willing to do the work.

• It's generally considered bad form to talk about human operant conditioning, so I will point out the following ostensibly-irrelevant-to-humans fact about animal operant conditioning for no apparent reason whatsoever: it helps to reward compliant behavior and to not reward non-compliant behavior. (Actively punishing non-compliance has negative consequences in many cases, though.) Also, the more obviously the reward is connected to the behavior (for example, the closer they are in time, and the more reliably the latter entails the former, and the more reliably the absence of one entails the absence of the other), the stronger the conditioning effect.

• Another ostensibly-irrelevant fact about animal behavior conditioning is that intermittent reward establishes conditioning that is harder to extinguish. This also allows for shaping -- once a pattern of behavior is established, reward only compliance that crosses a certain threshold.

Convincing someone else to work towards something is like devoting another lifetime to it, or doubling your efforts. And you only need to convince them once.

Evangelism!

So there’s two things I want to learn how to do: 1. Convince people to try and save the world

It is a tricky proposition. The world has existed for billions of years, and doesn't look as though it is at much risk. There are billions of humans on the planet. Our species is doing spectacularly well.

There are lots of people trying to convince others that the world is at risk. Resource shortages, a climate apocalypse, nuclear warfare, technological meltdown.

One problem is that most of them are transparently after your money and time - and just want to use a superstimulus to get hold of it. Humans are relatively vulnerable to manipulation using fear - and an apocalypse is a fear superstimulus.

Another problem is that most humans - like many other animals - are fairly self-interested. The coming apocalypse is usually a large collective action problem that most individuals are poorly-placed to influence - and poorly-motivated to try to influence.

So, people build up a memetic immune system that rejects this kind of material.

Making messiahs is a traditional problem faced by religions. They have many of the best tricks for overcoming people's natural defenses:

Get to people when they are young. Use authority figures. Use sex. Use scripture. Sever ties to the family. Make sure they have no money - and are dependent. Invoke powerful super-beings - and make sure they are on your side. Eliminate doubt. Employ inspirational speaking. Make sure that their eyes shine.