1. If you need the police to investigate a possible crime, investigate a defensive shooting, etc., and you contact them, the rule still applies: You do not talk to the police without the presence of an attorney. In practice, a police officer will not make a statement to IA until at least 24 hours have passed and his attorney is present.
2. If you are approached by police, remember that, in most every state, you are not required to present identification papers unless you are engaged in a permitted action (driving).
3. I don't know about other states, but in the Great State of Alabama, the officer must have RAS that you have committed, are committing, or are about to commit a crime before he can demand of you your name, address, and an explanation of your actions. (Ala. Code 15-5-30) Notice that there is no requirement for you to present an identification document.
4. Bottom line: If an officer approaches you with a friendly greeting and attempts to engage in a friendly conversation, that is one thing. If that same officer turns the friendly conversation into a de facto interrogation, then it is time to tell him, "I don't answer questions. Why am I being detained?" If he says you are not being detained, turn and walk away without saying anything else.
I exchange friendly greetings with several different officers on a daily basis and especially on Sunday morning when I exchange greetings with the officers on traffic control outside my church. Were those officers to start interrogating me, it would become a one-sided conversation very quickly.