Helping the Red Cross is simple. You just have to bleed. That sounds scary to some, but it's a lot easier than you expect. Most donations take about an hour. During that hour, a nurse will take a small sample of blood for testing, and then place a small needle in your non-dominant arm. Then you get to sit back and read a book, or watch Youtube videos, or swipe right on pretty people from Tinder for about 50 minutes. You also get free food and a coffee afterwards. Once the needle is in, you barely feel it and soon forget about it. Some people are scared of the pain. I want to stress that the pain is very quick and very light. If you have ever waxed your legs, you've been through a lot worse for a much dumber reason. A brief moment of pain, an hour of relaxation and a free feed will save three fellow Australian lives. Everyone needs to metaphorically and literally roll up their sleeves, call 13 14 95, literally roll up their sleeves and help save some lives.
Consider existing charities. Talk about their impact. Personalise their impact. Make sure the audience has actionable advice. They need to be able to actually do the thing you are suggesting. Try to tailor your techniques to your audience. In the example I have written, I could decide to challenge men and their masculinity, but doing this may actually hurt the overall appeal of the piece. I have to think about where I would publish my piece to know if this was a good decision.