What is the correct way to interrupt a repeater conversation to seek assistance in a distress situation?

When you need to interrupt an ongoing repeater conversation for an emergency, the most effective method is to wait for the brief pause between transmissions, state your call sign, and announce your situation. Repeaters often have slight delays, so waiting for the pause ensures your transmission won't 'double' (clash) with another station's signal. Repeatedly shouting 'HELP' or trying to talk over top of an ongoing transmission usually results in interference, making your signal completely unintelligible to those listening. Clearly stating your call sign and situation during a natural break allows the active operators to hear you and immediately yield the frequency.