"How can I determine through word, thought and action that people truly care about me?"

I don't think there's a surefire way to tell. One thing I look for is a person who makes an effort to come to me, they don't expect me to do all the seeking.

That said, I care a lot about the people I get close to, but I don't always have the energy to be there for them 24/7. Even when I can be there for them, there are limitations to what I can do for them, and sometimes I make it worse by trying when I'm unable to help. I think they key is being able to determine intent.