Brain Food: Your Route to the Top - Constructive criticism
Instil trust. Criticism can be a bitter pill to swallow, so sweeten it by showing that you're trying to help the person, not looking to feed your own ego.
Know your aim. Work out what you want them to do differently, and keep this in mind while you talk to them.
Think right place, right time. Have the conversation as soon as possible after the incident, so that the events are still fresh. If it's a sensitive issue, take it somewhere private.
Set the scene. Make it clear from the outset what you need to talk about.