Giving praise to what a person does must be kept in check. Providing too little of it will make someone feel ignored. Be generous about it but with just the right amount. Too much praise on the other hand keeps someone stagnant and standards will be weakened. Acknowledging someone because he does something he is expected to do is not helpful to his growth when done many times.
Giving praise, as well as criticism, are great tools in motivating people. But always remember to use it with the right dosage.