Observe what it is and praise that person for it. Sometimes more effective than praise in general is to identify and express appreciation for a specific job well done. This kind of recognition is especially welcome to anyone who has worked hard to achieve something. Look for opportunities to commend people publicly. Personal praise is good, but to commend a person in a staff meeting of peers or in front of a class is even more gratifying to the recipient.
People enjoy seeing their pictures on the wall, or their names on a plaque.
Handle reprimands with care. In almost all cases, they should be done privately. I like to call a person in and begin with mentioning something which the individual has done well. Then after a discussion of the offense, I cite some similar experience of mine, or a mistake I have made before pressing the point. People should not always be mollycoddled.