Interrupting people when they are in the middle of an important conversation is one of the most annoying things to do. It shows that you have zero knowledge of social dynamics which will lead to unpleasant social situations.

When you approach a group of people while in a conversation, pay attention to their bodies. If they turn only their torsos and not their feet, it means they are in the middle of an important conversation and they don’t want you to interrupt them.

If they turn both torso and feet, it means you are welcome. This is extremely important, because the right timing in such situations may put you in a position of advantage, especially if the conversation was boring for both sides.