When praising an entire class of students, it's important to be specific. For example, if you're addressing a very young class of children, it might be best to say to them, "You did a marvelous job lining up to go to the cafeteria, and you were extremely quiet and polite. That is great!" By making the praise unconditional - by not saying something about doing it again tomorrow or perhaps, "That's how you should line up every day!" You are making the praise more effective and without conditions.
When praising an individual, it's also important to keep praise personal, specific and unconditional. For example, if a student in your classroom participated in class by reading a part aloud in a play, you can say, "Great job reading the part of Juliet today!" That praise is specific, unconditional and personal.
Taking conditions out of praise is perhaps the best thing to take away from these two videos as I feel I have seen this, especially in younger children.