This is a very personalized question, wanting your specific ideas, but I can give you a basis to build on and some examples.
When we are talking about population-based change, we are usually targeting an entire community, not specific groups. However, the change is supposed to help individuals make better health related decisions. Some examples include:
- Raising taxes on tobacco products. This creates an incentive for people who use these products to start moving away from this habit. It becomes too expensive to maintain, so people can no longer afford this habit.
- Creating more walkable neighborhoods. A lot of lower-income neighborhoods have the disadvantage of low quality or no sidewalks. This can make it difficult for individuals in that community to be physically active, making them more reliant on cars. An intervention would be to educate the general public through social media and print materials. This awareness can drive the population to advocate for the city to improve the walkability of the neighborhoods.
These are just a couple examples. The idea with population-based interventions is that you are using a wide scope (social media, paper handouts, policy change, financial incentives, etc.) to encourage people to make healthier decisions in their daily life. The key is to making this change successful is to make the healthy decision the easier one. You want people to be more physically active? Create useable/ all-ability sidewalks and parks in neighborhoods. You want people to slow down in neighborhoods? Get the community together to create a traffic circle, building their investment in the safety of their streets. Want people to stop drinking so much high sugar drinks? Add taxes to increase prices, take them out of the vending machines in schools and workplaces, give people healthier alternatives.
In general, brainstorm a healthy issue you want to change and then how you can make the healthy choice the easy one.