I know all about selecting the correct target market for a product or service, but I've never seen a methodology for deploying for an audience that I can AFFORD. I wonder how much money I've wasted? I better not think about it too much.
Bar & Line: How to Identify Your Audience, 2020-Mar-19 by Duncan Geere
You have limited resources to reach people, and you need to deploy them carefully to maximize your impact.
By identifying the goals of your project, you can immediately narrow down your audience further. Think about who's most likely to be do the things that you want them to do - who'll have the time, inclination, and ability to act on the information you're sharing. These people are much more valuable to you than those who don't.
For example, following on from the last step, you're looking for people among the aforementioned groups who regularly donate to charity, and who actively use social media platforms. These are your core targets. They're interested in your subject, and they have the ability to do something about it. Sure, maybe people outside of those groups can do something with your information, but they're less of a priority because the likelihood they'll act is lower.
How can you reach them?
Finally, consider how you can reach these core targets. What tools and resources do you have at your disposal to get your work in front of their eyes?
This is the beginning of a full marketing and PR strategy, of course, but it's important to consider here because if there's no realistic way of getting your work in front of a particular group of people then it's not worth wasting any time targeting them. Concentrate instead on what you can do.