Gently, I think. I like to focus on what we can do together, not on what they shouldn't do. It's a bit of a mind game, but phrasing things in terms of possibilities and community goes farther than discussing remedial actions-- what people need to stop doing before we face horrible consequences.

Granted once you've got them on board, we can discuss the harder subjects that might require we make less fun changes to our lifestyles.

I plan to indoctrinate introduce people in my neighbourhood to solarpunk and grassroots activism by sharing produce from my garden, as an example. Once I have a good rapport with them, it'll be a lot easier to convince them to make changes. It's a lot easier to listen to the nice person who gave you a basket of broccoli than it is the person who slashed the tires of your gas-guzzling car. Beyond that, I think just being an example of how solarpunk communities can work is convincing enough.

(Note: I don't necessarily have an issue with more in-your-face protests like slashing tires, but I do think they serve a different purpose than getting people into a community)