Actual Discussion

What would you classify as effective forms of activism?

• Good activism is a very careful balance between making people uncomfortable with the status quo and making people uncomfortable with you, the activist. (This is, tragically, where much modern activism fails, largely, I think, due to the pernicious influence of "social" media and the echo chambers it builds.)
• Good activism is about people, not ideas and ideology. If you can't tell a story about actual, real-world people you can touch and talk to in your activism, you're not doing it right.
• Good activism comes from a default position of being for something (and as a side-effect perhaps against something else), not from a default position of being against something (seemingly never paired with being for anything else).
• Good activism is grass-roots, not corporate or government, in origin. Indeed if a corporation or a government wants to "help" your activism, look very carefully at what you're doing; you're likely doing something wrong that the status quo likes.
• Good activism is labour. It's hard work, done by boots on the ground, not keyboard warriors flinging hashtags around and doing dog-piles. Hashtags and "awareness" have their place in the process, but if you're not labouring, you're cosplaying activism, not doing it for real.

What are ineffective forms of activism?

Reading between the lines above (or just reading some of the parentheticals or antithetical clauses):

• Activism that causes people to be afraid of the activist more than of the change is ineffective. Trashing city blocks, for example, (unless a prelude to actual, violent revolution) is not going to change anything in the direction that activists would like; it is indeed likely to cause a backlash.
• That being said, if your activism isn't making people uncomfortable with the implications of the status quo, it's equally ineffective. "Polite activism" is an oxymoron. Those who call for courtesy in activism can get fucked. (See what I did?)
• If your activism is nothing but negatives (thou shalt not this, thou shalt not that) your activism will be ineffective. "STOP BEING RACIST!" is ineffective because most people don't believe they are, no matter what the actual truth.¹ ² You're just going to harden the opposition. Arranging dialogues with people of other cultures, holding up positive outcomes from integrating with them, etc. is far more effective. It's just a whole lot of work too. Which brings us to...
• Lazy activism ("slacktivism") is absolutely, positively, 100% ineffective. Slacktivists do more harm to their purported causes than do the actual enemies of said causes. If you're not willing to get in and get your hands dirty, get your back broken by the labour of proper activism, just sit it out. Half-assed hashtag-slinging and social media dog-piling just makes your cause look lazy and bad.
• Trying to shortcut activism by accepting aid from the powers that be (PTBs) in the corporate or government world is basically neutering your cause. Don't do it.

How does a group know when their mission is achieved? What if the mission is ambiguous or changes over time?

If I had the answer to these and an extra $50, I could buy a cup of coffee at Starbucks.

Do you feel they stop too early or too late?

Both.

#MeToo stopped way too early. Once the hashtag was slung and some serious shit started to hit the fan, feminist groups the world over should have pushed hard to ensure that abusers faced consequences. And some did. Before the weight of slacktivism dragged it down and made it part of the background noise. There's still gender-based abuse in all walks of life. Women (chiefly, but not solely) still get pressured into things they want no part of. But #MeToo was a passing fancy of the X/Twitterati who've moved on to other things leaving the actual labour of proper activism undone and unsolved.

On the other hand we have Greenpeace. An old-school activist organization that was against nuclear testing. (That's the "peace" part of "Greenpeace".) Once nuclear testing was stopped, they kind of had no real reason to continue, but press attention and money are addictive so they pivoted into a general environmental stance and carried on. Now I'm not going to cast shade on them for this, but I will cast shade on them for keeping that anti-nuclear stance to the point that they're actively harming the struggle against climate change. They're a bunch of people driven by an entirely-justified '60s- and '70s-era fear of nukes who are now dinosaurs fighting the wrong fight in the face of the global warming catastrophe. They should have stopped earlier on and let others take up the torch.

¹ Lest you think that I'm exaggerating, I'm going to drag up two spectacular failures of the western left: Brexit and the election of Donald Trump. The "Remain" camp of Brexit had only one real coherent, repeated message: "Vote 'Remain' or you're a racist." In the mean time the "Leave" camp fought on (distorted, inaccurate, or just flatly made-up) factual issues. SURPRISE PIKACHU FACE! Brexit happened. And I draw the line for that straight to the idiots fighting for "Remain". Then, only a few months later, after a similar campaign of "Vote Hilary or you're a racist!" ... SURPRISE PIKACHU FACE! Donald Trump got elected. Because the western left never seems to fucking learn!

² EVERYBODY is racist to some extent or another. No exceptions. No, not you reading this. No, not me writing this. No exceptions.