What is the proper way to join a conversation on a repeater?

When you want to join an ongoing conversation on a repeater, the correct etiquette is to simply state your call sign during the brief pause between transmissions. This politely notifies the current users that someone else is on frequency and wishes to speak. Amateur radio has strict guidelines regarding priority traffic. Saying 'break, break!' is exclusively reserved for urgent emergency communications; using it casually will alarm other operators. Overriding someone by increasing your power is considered malicious interference and is strictly prohibited.