I always stop and ask if anyone needs help. About a month ago I saw a woman on the side of the path with her bike upside down. She was trying to figure out why her handle bars were loose. Turned out that her stem bolt was loose. She had no tools and was about to start walking home. I tightened it back up and sent her on her way.
Another time I was riding in the dark along a road with no street lights. I saw a bike go by and heard something fall and hit the ground. I went back and it was a woman who had her light fall off and she was trying to find the parts. I took off my headlight and found everything in the grass and helped her get it back together. She thanked me and said you would think my son would have stopped and seen what was wrong. He was up ahead of her on the trail and didn't have a clue she had stopped.
Last year on the hottest day of the year I saw a guy fall off his bike up the pathway. At least 4 people rode past him without even slowing down. He tried getting up and stumbled a few times. I helped him off to the side of the path and gave him some water. He was with a friend and they had both been drinking and were on their way to a Paul McCartney concert. After drinking some water and resting he was back on his feet and he and his friend started walking.
I can only hope if I ever need help someone else will be willing to assist.