I know a lot of folks don’t like protest marches or don’t think they are useful. But they are IF you then get more engaged.
Call and write your elected officials. You can have more impact locally in a lot of cases so don’t just call people in national office! You’ve probably got a mayor, city councillors, maybe a county council, probably multiple state legislators, a governor! They all matter a lot and people are generally even less engaged in state and local politics. Pick a couple issues (or even one) you care a lot about and find out what they are all doing, then call and write.
Write media outlets about their coverage. Subscribe and pay for some media if you can. Yes they will make mistakes covering politics. Write them when they do. Mention you are a subscriber.
Show up to local activist groups. The local Democratic Party needs and wants you to show up. They have meetings where they decide what to focus on and who to support. If you’re conservative but don’t like some of what Republicans are doing, then please, please show up. Your voice is needed. I don’t believe we are as polarized as it seems — I just believe the most extreme voices control the parties. If party politics isn’t your thing, find a local group on a cause you care a lot about and show up to their meetings and events.
And if the main way you want to engage is to push back against Trump and radical changes by Republicans controlling all branches of government, there’s a guide just for that.
Finally, think about running for office or supporting a friend do it! Politicians really are just people like you. I believe most do actually mean it when they say they run for office to make peoples lives better. You can too.