Whether you are the one giving or the one receiving criticism, these types of conversations can be difficult to manage. Luckily, there are a few simple rules that can set you up for success whenever you have to give criticism.
First, criticism should always be delivered in private. Correcting a person in front of others activates their defense mechanisms. No one wants to look dumb, so it is likely that the person you are correcting will dismiss what you say. It could even lead to animosity between you and that person if they think that you went out of your way to embarrass them or “put them on blast.” The best approach is to make a note of the behavior you wish to correct and then meet with that person in private to discuss the issue.
Second, criticism should always be delivered in a calm manner. Yelling gets you nothing. In the worst case, you lose credibility and the person blocks out the message behind what you are saying. In the best case, you intimidate the person into complying. However, you now have a person doing what you say only because they are afraid of you. This builds animosity, hurts collaboration, and can poison overall productivity by creating a culture of fear. Make sure, if the behavior you are trying to correct upset you, that you take time to reign in your emotions and are capable of talking about the subject calmly and clearly.
Third, conciseness and simplicity are your friends. When delivering the criticism articulate your expectations, explain how you perceived their behavior, and point out where the behavior in question failed to meet expectations. After, it is important to ask questions about what steps should be taken in the future to correct the problem. If the person you are correcting comes up with their own solution, then they are more likely to own it and show real change in the long term.
NOTE: During the conversation it is important to understand how the person you are correcting perceived your expectations of them. Just because a behavior you did not like occurred does not mean it was done with the intent of failing expectations. For example, your significant other might hate mushrooms. However, if they never told you, it would not make sense for them to get mad at you when you show up for dinner with a mushroom pizza. That is because the expectations regarding the correct behavior were not clearly established. So make sure to set clear expectations. Additionally, be open to the idea that expectations you feel were clear may not have been clear to the individual who performed the behavior you now wish to correct.