I've complained about the tactics scammers use. Short version: appeal to emotion + populism = win. This works as well for baseless causes as for worthy ones, it seems; the odious universal basic income* has got onto the Pirate Party's crowdsourced manifesto as a thing they'd like to see in the future despite all the problems I've already pointed out. Well, the will of the people must be respected.
That said, if you've got a policy, cause, or other agenda to promote and you want to get people on board, you may find that appeals to emotion and populism aren't working for you. What then?
Get a clue
I've been in arguments online nearly every day this week over social justice causes of one kind or another. I'm not saying I won, but if the other guy backs off without providing a convincing answer or makes a huge fool of himself, I tend to think I did. My perceptions, right or wrong, are not at issue here, it's whether you're achieving your aim of getting people on board with you or merely airing your opinion. I've got a few ideas that might help.
Make a plan
Sit down and carefully consider what your message is about. Suppose it's "Save the tiger." Cobble together some fact-based talking points, e.g. destruction of habitat, poaching, the impact of Chinese medicine, etc. Test your sources to avoid accusations of confirmation bias, then propose a solution so you can give your audience an opportunity to make a difference.
Test your arguments
Post an attention-grabbing comment online, e.g. "One tiger is killed DAILY for use in Chinese medicine! #SaveTheTiger"
Get ready, because at least one person is going to pop up and ask you to substantiate your claim. "I got it from this website" is not likely to hold up, so check your sources and make sure they are trustworthy. Assume that every point you ever make will be challenged, so have your talking points and evidence ready.
Make an asset of dissent
One problem I'm increasingly running into with certain people is their narrow-minded authoritarianism. Many of them seem to interpret dissenting views as a personal attack on themselves and their cause, which makes it impossible to have a civil, solution-oriented conversation about anything with them. Do not fall into that trap. If your cause is just and your evidence trustworthy, you've got nothing to be defensive about because the truth is on your side. If someone wants to argue with you, let them. Answer their questions as fully and completely as you can, with the greatest courtesy.
If they are successful in contradicting you, award them the point. When a musician pointed out that selling merchandise doesn't work for all musicians I realised he's right, so I told him so. Then I pointed out that his problem was not being more popular, in which case he'd shift more of everything. Remember, no one has an intrinsic right to unquestioning agreement from everyone.
Be willing to consider other points of view, even when they're demonstrably wrong. It makes you look reasonable and may win the other person over. Then again, it might not, and that's still okay. Their audience sees it, too. Regular readers may have noticed that I only have these conversations with obscure hobby artists, not those who make an actual living from their work.
Be self-controlled and alert
Some people just love to troll. Guilty as charged! Self-important authoritarians are a favourite target, though sometimes I prefer to drive by, prod them a few times till they make fools of themselves, then mute them. Turning my timeline into a pavement pizza hurts them more than it hurts me because it's off-putting to potential supporters, and since I can't see what they're saying I'm not affected by it. It's important to keep control of yourself; you can't control the narrative so don't bother to try. People will think what they want to and there's not much you can do about it.
Stay on-message and be willing to learn from your mistakes as stonewalling or repeating failed arguments in a loop tends to alienate people. If you read through my posts on Basic Income you will find that I use the proponents' talking points against them by finding weaknesses in their arguments. That's because I learn from dissenting points of view. No one has successfully put me on the back foot over middle-out, though one man tried. There seems to be no weakness in my arguments... but that's because they haven't been put through the mill yet. Look out for opportunities to either fine-tune your own position or patch the holes in it. Don't stoop to name-calling or making rude remarks or you will lose credibility.
Get on top
Once you have established credibility by effectively arguing for your cause, you need to leverage your popularity by discussing and developing your ideas. No policy, etc., is so perfect that it doesn't need the odd tweak. It's hard to argue against logic, which is why the people I disagree with tend to make wild accusations, call me names, and are rude to me. I find that the less substance their arguments have, the more likely they are to behave like this. If your idea has substance, you don't need to lash out at people who disagree with you. Or patronise them or dismiss them. Leave a bit of room for the notion that you might in fact be wrong. Wiggle room is the key to success in any campaign.
Get people on board
Asking people what they think by sharing links related to the thing you hold dear can and does stimulate discussion. I often tag people and ask if they've seen a particular thing. The end result has often been a stimulating conversation. By being honest about what I don't know and asking for further information I've earned a fair amount of respect in the circles in which I move. Take a look at the Pirate Party manifesto and see if you can spot any of my middle-out ideas in there. I'm very pleased about this and okay, I didn't get everything I wanted but at least I got that. Of course, you realise that this was crowdsourced, right? That means people voted for a robust welfare state, raising the minimum wage, and increasing spending on infrastructure, education, and things like that? Okay, they were already on board with much of that but in this iteration they're more focused on those areas. When people you respect quote things you've said to them to their peers, that's when you've arrived.
Ideas and policies should always be flexible. When they're not, they fail because they don't take variables into account, and that's because there's no room in there for variables. This is why their proponents are obliged to rely on logical fallacies and emotional arguments to push their nonsense forward: they know full well it's nonsense. If, however, your ideas are fluid and adaptable, they are more likely to succeed.
Well I hope you find this useful, it's not an exhaustive list by any means but then, the idea is to get you to think about the way you come across online if you want to succeed at promoting your ideas. Good luck!
*I'm not a UK citizen, I'm Irish. Applying for citizenship doesn't guarantee I'd get it and I've been over this before, you know all my arguments. If you're still in favour of UBI nonetheless, I'd like to know whether or not it's due to this (and the other issues I've mentioned) not being your problem. It's not fair to jump to conclusions, after all.