There are 50 missions in total, as you progress through the game each gets slightly more difficult and opens up different threat aspects (i.e. enemy agents killed on missions after India drop time bombs). The essential strategies however, are the same. There's no such thing as overkill really, and the more firepower you have the longer your agents will survive in the field if the shit hits the fan.
Miniguns tend to be the main weapon of choice. Adequate range and a reasonable fire rate offset the issues of weight if your agents do not have the version 2 arm modification or above.
IPA (intelligence, perception, adrenaline) control of your agents can boil down to two settings: either all up to maximum for the best combination of speed and accuracy and hoping your cyborg won't step blindly in front of a car, or all down to minimum if things are quiet and the available levels are too low.
The regions within each section of the mission guide are provided below:
Western Europe, Scandinavia, Central Europe, Eastern Europe, Urals, Mongolia, Kazakhstan, Siberia, Kamchatka, Far East
China, Pacific Rim, India, Iran, Iraq, Libya, Algeria, Arabia, Indonesia, Northern Territories
Western Australia, New South Wales, Mauritania, Nigeria, Sudan, Zaire, Kenya, Mozambique, South Africa, Alaska
Northwest Territories, Northeast Territories, Greenland, Yukon, Newfoundland, California, Rockies, Mid West, New England, Colorado
Southern States, Mexico, Columbia, Peru, Venezuela, Brazil, Paraguay, Argentina, Uruguay, Atlantic Accelerator.