Keep in mind that there are different types of conversations. Some that appear very accessible to join, and others that seem to be closed off to others. When you see people talking softly or speaking very close to one another, it is best to leave them alone. It most likely is a private conversation.
Watch a conversation for a brief time before joining in. Listen to what they are discussing, and feel comfortable adding your thoughts at a natural break in the conversation. After your comment, introduce yourself the others and apologize for breaking in. Most likely, they will pleasantly accept you into the conversation.
Listen quietly to the conversation for a moment. If it is specifically about a work situation or other private topic, go on to another group. If you do not know anything about the topic, but it interests you, do not feel uncomfortable just standing with the group and listening. If the group is discussing a topic that interests you in one of the more sensitive topics of religion, politics or sex, be careful of giving your opinion if it is contrary to those talking. As long as you do not come across forcefully and negatively, it is appropriate to express your opinion. Be prepared, however, for a backlash if everyone in the conversation feels differently.
Use positive body language when joining a discussion. Have a pleasant look on your face and your arms uncrossed. This way you are inviting others to welcome you. If the topic is of interest and you are not making any comments at the moment, wait for a break and politely ask, "May I join you?" If you see any negative body language or get the sense that the group does not want to be interrupted at the moment, do not feel offended. Nicely say something like, "I'll join you later."
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