I think that to help out others whenever you can without compromising your personal safety* and especially that of your family, you just do it. But you have to be mindful of your surroundings and the situation.

While driving, I usually don't stop, but call 911. Getting out on the road can be a very dangerous thing. Response time is pretty good. If I see somebody hurt trying to get out of their car I will probably stop to try and help.

* There are times when risk to personal safety is probably required. For example, I once saw an elderly lady faint and fall into the road into oncoming traffic. I ran onto the road to get her off it. The dead weight of an unconscious person is pretty unwieldy, so I mitigated my risk by risking another pedestrian. I yelled over to him as I was running out to the lady to come and help me carry her off the road. There is a lot of power when you point to someone directly and say, "YOU! ..." After we carried her out of traffic, I pointed to a guy with a phone and said, "YOU! Call 911!" Especially when you look them in the eye too, there is no mistaking you are talking to them.

Anyway, I am going off track. It's good to do something good for others without regard for your own reward. Because the rewards WILL come. Even if it is just a good feeling. Just be careful.