This is the tutorial mission. If you’re new to the franchise, it’s very important. If you’re a fan of the first game, chances are you play a lot of multiplayer and your skills haven’t even had time to rust. Either way, your first objective is to school the native military on how to shoot. You’ll start out spraying from the hip and work your way up to shooting down the sights, snap targeting, and shooting through light cover. It’s simple stuff.
Once you’re done there, make your way over to the pit. This section is a lot like the training exercise in the beginning of Call of Duty 4. Based on your time here, the game will recommend a difficulty level. You have no obligation to choose their recommendation, though.
When you get to the pit, you’re ordered to pick up a Desert Eagle. You can then choose between a SCAR-H Foregrip, MP5K Holographic, ACR Holographic, or M9. Give them each a try and decide which one you like best. After you find something you like, practice switching between your primary and secondary weapon a few times. Switching from your primary to your pistol is always faster than reloading.
Once you’ve got your weapons, it’s time to show General Shepherd what you’re made of. The training exercise is simple, just make your way through as quickly as possible while eliminating the targets and sparing the friendlies. At the halfway mark, you’re forced to kill the target with a knife attack. It’s a good technique to learn, anyway.
Finish the pit in under 30 seconds to get the Pit Boss achievement/trophy.
Even if you’re a season Call of Duty player, playing on anything above regular difficulty for your first playthrough isn’t a good idea. But hey, it’s your virtual life! Plus, you can always change the difficulty during your playthrough.
Completing this mission will get you the Back in the Saddle achievement/trophy.
Article from Gamersyndrome.com