something I worry about

Ok so I am sure I am not the only parent out there who has this question, HOW DO YOU TEACH YOUR CHILD TO NOT BE A FOLLOWER? at least I hope I am not the only parent because then this would be pretty embrassing :) I have just been noticing latley that kaden will say to me"well mom so and so is doing it" but he is not wearing his helmet" mom go away I am with my friends"
So as any parent would naturally do is WORRY! I tell him all the time to not worry about what other kids do, but do what he has been taught, but I am not so sure he really understands me.
Why is it that when kids get older they don't think they need to set the example for those that are younger by wearing helmets and not riding their bikes in the street and maybe having a little more respect for parents.
Kaden does good sometimes, but I feel like I am always yelling his name and getting mad at him because he just does not LISTEN. So I was wondering what you have experinced with your kids and what you think might help.... I can't help but worry when he gets into kindergarten and older grades how will he respond to other kids choices? What kind of things can I do better to help him now? Of course it is only natural that a parent worries about their kids, a few times I just notice that what I have been teaching him has gone in one ear and out the other.... are kids really born with ears? (I wonder sometimes) well i better go for now, I would love to hear your thoughts.... Until next time....