When you notice something positive and helpful, you may want to start by providing a positive, encouraging consequence to what they did or said. This can be as simple as telling them how much you noticed and appreciated what they did or said. It could be highlighting those things to others. Then you can provide antecedents for the future by helping them remember their own good examples.
When you notice something negative and unhelpful, you may not want to punish it directly. Sometimes being right hurts your relationships and limits your influencing options going forward. Instead, consider not reacting at all to the specific instance, but, instead, helping them see other, more positive ways of doing things in future situations.