There are not necessarily very effective ways, by the very nature of fighting against a leviathan, nor do I pretend to be an expert (or even knowledgeable) on the matter. There are historians who claim, correctly I believe, that no revolution against a united ruling class has succeeded without outside military and diplomatic support since before the French Revolution.

Now, you might not want to go for a full revolution, but splitting the ruling class is always a good idea. This is a goal, hardly specific instructions, but you need to know where you are going or (as Yogi Berra said), you might never get there.

In countries like Russia, I see that when people suspect that the government engages in fraud, they use poll watchers, and sometimes try to get out the vote to vote against government-favored parties like United Russia - if not to diminish the power, in order to force the government to commit more fraud and embarrass itself. Revealing government corruption also does a lot of good.

Orwell, I believe, said that all governments rule by fraud and force. Once fraud no longer works, they are forced to rely solely on force, which simply works less well than the combination. So stripping away the fraud and denying legitimacy to the regime does a whole amount of good. I think the main problem in the US is that the majority of people regard the regime as legitimate. That is because, contrary to the claims of Trump supporters who make dubious claims about 'massive fraud'; it still has plausible deniability. Forcing them to commit massive and open fraud, if that is what they are doing, will inevitably tarnish their reputations even more. Make no mistake, even those who rationalize all shenanigans to keep Trump out would not approve of open fraud, if only because it tarnishes their self-image for lack of minimally plausible deniability.

Without regime legitimacy, soldiers shooting on demonstrators are not 'upholding constitutional order' or 'protecting democracy', they are murdering their fellow citizens who are fighting for their rights. There have been many times when soldiers simply refused, or that the regimes did not have the confidence and thus collapsed (but unfortunately, it seems that they were mostly conscript armies).

These are a whole lot of words to say, in retrospect, rather little. But maybe some pointers in directions we should be thinking about. But one thing that is very bad, is not voting or giving up, at least in the US. If someone thinks that "they will steal the election anyway, so why bother voting?", like I always say, if they think the election is worth stealing, then it's worth voting for him - aside from the other benefits of forcing the regime to commit fraud (if that is what it's doing, IMO they rigged the election legally with mail-in voting and Hunter Biden shenanigans, not by stuffing ballots).