How to gain college credits by volunteering?

Hey everyone, I just wanted to ask a few things. I'd really like to be involved in things of my future, but I just don't know where to start. I grew up from an average family, but soon enough my family's finance started going down hill. I'm still very young, 14 to be exact. I want to do something with my future, either it being a social worker, a veterinarian, an author, an addict counselor. I want to do something that will actually impact someone or somethings life. Tell me, what can I do to help raise those advantages? What can I do such as volunteering? What are the possibilities? Thankyou, answers would be helpful (: