It's usually more effective to have specialized interests, since it's very rare to have agreement on multiple issues across a large population (this should be intuitive to the HN crowd, where every issue you add doubles the number of potential positions, even though they're not random).

Find an organization that already exists and get involved in it. If one doesn't exist, create one.

For packaging, you'd have a few potential avenues: 1. Work to build support politically. Even small groups of 30-40 people (or smaller) are very attractive for local politicians to meet and speak with. 2. Reach out to companies directly. 3. Get earned media (possibly in conjunction with 1 or 2).

If you have small, achievable, reasonable goals, then it may even be a win-win scenario for all of the above, which makes it easier to make progress. For example, you could have a campaign goal of reducing x% of packaging to reduce y tons of waste.

It could be positive media attention for a company to say they've worked with a group like yours (or a small local company!) to reduce packaging and help save the environment (and it may even save the company money).

Finding ways for everyone to win and creating a big tent (as opposed to trying to influence by vilifying) tends to be more successful, in my experience.