Ok, when you get to the Tank Hangar and you've stopped following the rats, stay still. You should see an opening where you can sneak out of. But there is a solider walking around. Sooner or later, he'll stop right in front of you. You should have your tranquilzer out. Aim for his legs and shoot him 2 times. He should fall asleep then. Crawl out of the vent and stand up. Take out your Socom and go into first person view. Just aim at his head and pop a cap in him. It's an instant kill, it works well when you knock down an enemy or put them asleep.

If you put on your gas mask while under water, your O2 gauge will decrease slower, just like it would while in a room filled with gas.

While fighting the ninja throw a chaff grenade and he will freeze letting you hit him.Once you hit him he will falls to his knees and won't get up until all the yellow dust from the chaff grenade has fallen.

When you hang from a ledge, do 100 pull ups (L + R). They have to be good pull ups. Grip Lv "3" is the maximum grip Lv.
Tip: In grip Lv1, you can only fit 4 good pull ups. Dont rush it. Once Snake does a good pull up let go of both buttoms, not just one.

First off, throw a chaff granade before REX has any chance to do anything. After the radar is jammed, aim for the cirrcular disk thing on REX's right shoulder and hit it with your Stinger. This will continue until an intervention from the ninja. In the second phase of the battle, chaff's will be useless, all you be to do is aim at Liquid in the cockpit and fire away. A very easy Boss.

At first Mantis will try to use Meryl to hurt you, but don't shoot her. Instead just whack her in the head with your fists. After Meryl is incapacitated, Mantis will teleport around the room and harm you with various projectiles, but if you try to shoot him he will say, "I can read your mind!", and dodge the shot. Quickly pause your game and change which port your controller is plugged into, then resume the fight and Mantis will no longer be able to "read" your shots. He will agian try to use Meryl against you, but just repeat the same steps as earlier. (Note that Mantis might begin to dodge your shots after about a minuete and a half after you switch ports, so just pause and switch again.)

During the Ninja boss fight, shoot the Mario figure on the desk to gain extra health.

When your life is orange/yellow coloured and your bleeding, there is an easy way to get your life back to the green colour so you aren't bleeding and your life is decreasing!

Find a locker, open it and hide in it as you would when your hiding from an enemy and your life will restore itself to the green colour.

This will happen instantly, as soon as you get in the locker.

But be wary, your life will not restore itself to full but it will go to the lowest ammount possible that is green!

For easy girp level, all you have to to is,when climbing down the wall (with the rope you found eairler) stop on one of the places to walk and walk a while and not long you will have level 2 grip then three if you want.