You have to make it memorable and you have to make people want to say it of their own volition. And so what doesn't make them want to say it is doing a favor for a corporation. What does make them want to say it is they want to bring joy to somebody else, they want to make somebody laugh, they want to appear interesting, or they want to project some part of their identity.
Messages spread when they serve the messenger
Growth → Acquisition
You want to make it something that a second-grader could understand. You want to minimize the cognitive burden on the recipient. So it should be something where they're not having to expend any extra energy understanding the thing, where it immediately paints a picture.
The word remarkable means worth making a remark about. So I'm not talking about coming up with some viral video that's ridiculous in its gimmickry. I'm saying if you make something where the person's life gets better if they talk about you and you know in advance what you want them to say, then they are more likely to say it.
If people only read the title and the button, they got it. It can't be like, 'Wouldn't you like the next President of the United States to blah blah blah?' And then the button is like, 'apply.' It's like, apply for what? Now I have to go read the thing and I didn't get it.
People don't talk about a product doing exactly what they expected it to do. They talk about a product doing what they didn't expect.