What commonalities are there, in terms of techniques, utilized for investigational approaches across all of the federal organizations? (i.e. FBI, DEA, ATF, CIA etc)
Before discussing the common techniques shared among federal law enforcement agencies, it should be pointed out that the Central Intelligence Agency is not a law enforcement agency and does not conduct criminal investigations per se. It is an intelligence agency the primary function of which is to gather information on foreign countries, analyze that information, and provide estimates to public officials, mainly the president and vice president. To the extent that it gathers information on foreign governments, individuals, and nongovernmental organizations, for example, terrorist and organized criminal organizations residing abroad, utilizing some of the same surveillance techniques as domestic law enforcement agencies, it should not otherwise be included in the list of U.S. Government agencies included in the question.
The Federal Bureau of Investigation (FBI) is the principal criminal investigative agency for the federal government. Over time, it has developed very sophisticated techniques for investigating crimes, criminal conspiracies, and potential terrorist cells operating within the United States. Using electronic and photographic surveillance, informants, undercover operatives, and other means of gathering information, the FBI has been at the forefront of developing the techniques utilized by other agencies. While the FBI conducts investigations involving U.S. citizens who are victims or perpetrators of crime in foreign countries, it is primarily a domestic law enforcement agency.
The Drug Enforcement Administration (DEA) and the Bureau of Alcohol, Tobacco, and Firearms (actually amended to include "Explosives" in its title) have more narrowly-defined missions than the FBI, but utilize many of the same legal authorities and investigative and surveillance techniques as the FBI. One commonality with the ATF, but difference with regard to the DEA, is the degree to which the FBI actually gathers and analyzes scientific or forensic evidence associated with crimes for the purpose of supporting a potential prosecution in a criminal trial. The DEA and ATF similarly gather information and make arrests with criminal prosecution as the goal, but the DEA in particular is more active in cross-border operations. The very nature of drug trafficking and associated money laundering activities require a more active presence in countries where the drugs originate and from which they are shipped to the United States. The money laundering component of an investigation often draws in the Department of the Treasury's Office of Terrorism and Financial Intelligence, which works with foreign governments on money laundering investigations.
An additional federal agency that similary enforces particular laws -- in this case counterfeiting of U.S. currency -- is the United States Secret Service, which utilizes investigative techniques common to the other agencies. Because the governments of North Korea and Iran, as well as some drug cartels in South America, are known to produce counterfeit U.S. currency, the Secret Service conducts criminal investigations that usually involve foreign financial institutions.
As far as commonalities are concerned, the law enforcement functions as well as the surveillance techniques of these different agencies are very similar, and sometimes agencies cross paths when both are conducting investigations that lead in the same direction. Investigations have been jeopardized by the failure of agencies to work together.