Metal Gear Solid: Portable Ops - Cunningham

Elisa:
Successfully complete the game with a "Medic" rating of 80. Play the game a second time. Save the game, exit, then load your game and she will join you.

Major Zero:
Have a Metal Gear Solid: Digital Graphic Novel saved game file on your Memory Stick. Successfully complete the game, then play the game a second time. Save the game, exit, then load your game and he will join you.

Null:
Play through the game twice on the Easy difficulty setting, killing Null once with health depletion and once with stamina depletion. During your third session, start the game on the Normal difficulty setting. Get to a point where you can save the game. Save it, then exit the game completely not standby go to the main PSP menu. Restart the game, load your game, and Null will join you.

Para-Medic:
Contact her in the Comm Building after Roy is feeling better from his malaria. She will offer to help. Place spies in the hospital and wait. She will eventually become a side mission to recruit.

Python:
Instead of health depletion, use a tranq gun and stamina to deplete him. You will get a different intermission sequence and Python will join you.

Raikov:
After Snake is captured, do the missions as usual until the guest house. When you get to the guest house do not continue. Instead, place spies in town and wait. Do other missions until you get a report of a map. Retrieve the map and place spies in the wilderness. Keep waiting and eventually Raikov will need rescuing. Rescue him and proceed as normal.

Signet:
After you rescue Snake and rercruit Para-Medic, go into the Comm building again. You will contact Signet and he will offer to help. Place spies in town and eventually he will become a side mission.

Teliko:
Have a Metal Gear Acd saved game file on your Memory Stick. Successfully complete the game, then play the game a second time. Save the game, exit, then load your game and she will join you.

Venus:
Have a Metal Gear Acd 2 saved game file on your Memory Stick. Successfully complete the game, then play the game a second time. Save the game, exit, then load your game and she will join you.

Stealth Camouflage:
Successfully complete the game with a "Technician" rating of 99 to unlock the Stealth Camouflage, which allows you to become invisible for a limited time.

Defeating Null:
The times which you can shoot him with a non explosive are when he is reloading, turned his back against you, still looking for you, or sometimes while shooting if you are lucky. The best gun for this is the shotgun. When you actually get a shot into him, it will knock him down.

Defeating Python:
When fighting Python, lock on to him with L and shoot him when he becomes visible through the fog. Make sure to continuously back up, otherwise he will lunge forward and knock you down with his weapon. It is also a good idea to plant the TNT with a soldier other than Snake. By doing this, when you begin the fight you will start as the character you planted the bomb with. Then if your character dies, you will have the option of selecting the next player to fight with so that you can save Snake to finish the job after Python has been weakened.

The best weapon to use against Python is the shotgun. It will knock him down and you can shoot him again before he gets back up. Additionally, the shotgun deals a lot of damage but does not require you to do any fancy moves