A lot of what needs to be done is making sure that the Harris win is large enough that you can’t easily claim that a handful of ballots should be tossed and change the outcome. That means:
- Check your voter registration — part of the Republican strategy has long been invalidating registrations so people can’t vote
- Volunteer — nothing in the world quite like talking to people.
- Donate — money is used for everything from ads to voter turnout operations
- Organize; be prepared to turn out with others in your community to actively object to any effort to ignore your votes
Due to the way the Electoral College works (even when not being undermined by bad-faith actors) it is possible for a candidate to win the popular vote (i.e., get more raw votes than his opponent) and yet end up with fewer Electoral College votes thereby losing the election. This has happened many times, and I believe no recent Republican president has won the popular vote with the exception of Bush Jr.'s second run.