Simply make sure you pack up anything you bring in with you. If you're a mountain biker, give a heads up to hikers, with a friendly shout, when you're enjoying the downhills. If you see somebody littering, let the rangers know. If you see somebody walking their unleashed dog, but the dog isn't bothering anyone and is under control, do not let the rangers know. If you see somebody consuming anything you suspect they shouldn't be consuming, but they're doing it responsibly without bothering anyone, again I suggest not telling the rangers.
Rangers are usually very cool.
When they tell you to do something, it's often a good thing to do. So, be nice to them also. You're in the right place.