To find the second hidden Data Disc in the Cairo Trainyard level, go to the area where you see a gas tank is covered by two objects. You will see another gas tank on the other side of the fence beyond the first one. You cannot shoot it. Just throw a grenade and you will get a hidden Data Disc.
Defeating Bosses
A good way to lower the Boss' health in the driving part is to dodge the explosives and hold A to keep firing at the car.
Moscow: Defeating Jaws
The only way to hurt Jaws in the Moscow level is to shoot at the monitors or television until you cannot anymore. Then, try to trick Jaws to go in front of the broken monitor. Shoot him until he has been pushed back into the broken monitor.
Peru Facility: Mya's Holopuck
To find Mya's holopuck in the Peru Facility (or Andes mountain) level, complete the first stage. You will automatically go to the second stage, where you will start on a bridge or some kind of a walking platform. Go to the area where you see some green chemical pools and a bridge or a walking platform on the right side. Go under the bridge then move beyond it. You will see a secret area, where you will find a Hollymya +3. You will not be able to see or identify that area if you only stand under the bridge.