When you are giving someone credit for a job well done look them in the eye and keep it short, simple and focused on the behaviour of the person, i.e. 'You did a really good job of sorting out Mr Actor and his concerns over using the wind up gramophone'. This focuses on the acknowledgement of behaviour. If this was done with reference to the character of the individual i.e. 'Your people skills never cease to amaze me and that business over the gramophone was no exception' you could be in deep water if the next time you have to pull them up on their interaction with an actor and in reply you get 'Hey the last time you said I was great with people' it will be thought even if it is not said. This aside, whether praising or reprimanding anybody stick to the behaviour of the individual - behaviour can in most cases be relatively easily adjusted. The fundamental characteristics of a person are not so simple.