Today, let me discuss the initial, or first, contact with law enforcement. If the FBI, DEA, Secret Service or Homeland Security come to talk to you about something you may have done, beware. First, remember this is not a social visit no matter how friendly or cordial the agents may be. They are there for one reason only, to gather evidence in the prosecution of a federal criminal case. If the target is you, whether they say so or not, then it is in your interest to NOT cooperate with them. This should be done respectfully but firmly. For example, "Agent I do not choose to speak with you at this time, exercising my rights under the 5th Amendment of the U.S. Constitution. I also choose to have my attorney present and exercise my rights under the 6th Amendment to the U.S. Constitution." The choice of language is legally important and the U.S. Supreme Court has mad this very clear. My phrasing above, is based on several opinions by the Supreme Court as to how both the right to remain silent and the request for counsel must be stated to preserve those rights.
Also remember that it is perfectly permissible for these agents to lie, or mislead you while conducting this "interview". Doing so will not get them in trouble with either their agency or the court. I have had FBI, and other, agents admit lying to my clients to get them to say what the agent wanted to hear. These agents have freely testified to doing so in front of juries, so they have no fear of committing such conduct. You should be very careful and that caution should lead you to exercise the rights as stated above.