SNEAKING. This isn't a shooting game, even though there are guns in it. The whole idea is to not get seen. If you play it like a shooter you'll have a bad time, and you'll miss the best parts. On my Extreme run I went through most of the game without a single alert.

THE RADAR. Top right corner. The red dots are guards, and the cones coming out of them are what they can see. Stay out of the cones. When you get spotted the radar shuts off and you're on your own until the alert clears, so don't get spotted.

KNOCKING ON WALLS. Press up against a wall and tap the punch button, and Snake knocks. The nearest guard comes over to see what the noise was. Then you sneak around behind him, or wait for him to turn around and go past. It's the most useful trick in the game, and a lot of people never figure it out.

CRAWLING. Get down and crawl under things: desks, trucks, vents. A lot of the game is in the vents.

FOOTPRINTS. On the heliport and outside in the snow, guards will follow your footprints. Seriously. Look behind you.

THE CARDBOARD BOX. Get in it. Guards walk right past. I'm not going to explain why this works. It just does, and it's the funniest thing in the game.

CHAFF GRENADES. A chaff grenade jams electronics for a little while: security cameras, the gun cameras on the walls, and anything that locks on to you. It also jams your own radar, so you're blind while it lasts. Save them. You need them for two of the bosses.

RATIONS. They heal you. Equip one before a boss and Snake eats it automatically when your life runs out. In the cold areas they freeze, and a frozen ration doesn't work until it thaws, which it does if you keep it equipped for a bit.

01 REVOLVER OCELOT
The gunfighter. He's in a big room with a hostage tied up in the middle, and the hostage is wired with plastic explosives. The wires run around the middle of the room in a square. Do NOT shoot the wires, and do not run into them, or it's game over.
HOW: Use the SOCOM. Run around the outside of the wires, the same direction he does. His bullets bounce off the walls, so don't stand still. He has to reload after every six shots (he's got a revolver, he'll tell you about it), and when he stops to reload, that's when you hit him. Three or four rounds of that and the fight ends, in a way you won't expect.

02 M1 TANK
Out in the snowy canyon. A tank. You. Good luck.
HOW: Throw a chaff grenade first, every time. It messes up the targeting for the big gun. Then get in close, where the big gun can't really aim at you anyway, and throw frag grenades at the soldier sticking up out of the hatch on top with the machine gun. Don't stay in one place. When the chaff wears off, throw another one. Taking out the gunner is what ends it.

03 THE NINJA
In the lab. A cyborg ninja with a sword who can deflect bullets.
HOW: Your gun is useless here. It's a fistfight. Wait for him to come in close, then hit him with the punch-punch-kick combo. Back off, wait, do it again. Later in the fight he starts turning invisible. Keep moving, watch for the shimmer, and when he comes at you, combo him. It's really about patience. If you go after him, he wins.

04 PSYCHO MANTIS
The best boss fight I've ever seen in a game. He reads your mind. He'll read your memory card, too, and tell you what other games you play. He'll tell you to put your controller on the floor and then make it move. At one point the screen goes black like your TV changed channels. Your TV did not change channels. Don't touch it.
HOW: First, he takes control of Meryl and she comes at you. Don't shoot her. Knock her out with your fists or choke her until she drops, without killing her. Then Mantis himself: he dodges every single shot, because he's reading your mind through your controller. The trick is to unplug your controller and plug it into port 2. Then he can't read you, and you can hit him. (If you can't figure this out, call the colonel on the codec. He'll get there eventually.) After that it's just a matter of dodging the furniture he throws at you.

05 SNIPER WOLF (FIRST TIME)
In the long underground passage. She's at the far end with a sniper rifle and you're out in the open.
HOW: You need a sniper rifle of your own, the PSG1. If you don't have it yet, you have to go back for it, and the game makes sure you know that. When you look through the scope, it sways. Take diazepam and the sway settles down for a while. (Smoking a cigarette steadies it too, but it costs you life. Snake doesn't care.) Find her in the scope, wait for the sway to drift over her, fire. Then move, because she'll move.

06 HIND D
A helicopter gunship, on top of the communications tower.
HOW: The Stinger missile launcher. Lock on, fire, then duck behind something while it shoots back. It circles the tower, so you'll be running from cover to cover. Bring rations. This one is about volume: keep putting missiles in the air.

07 SNIPER WOLF (SECOND TIME)
Out in the snowfield, in the trees.
HOW: Same as the first time, PSG1 and diazepam, except now she's hiding in the trees and you have to find her first. Scan the tree line slowly and watch where her shots come from. Take your time. The second Sniper Wolf fight is the one that matters for the story, and I'll leave it there.

08 VULCAN RAVEN
In the warehouse, a maze of shipping containers, and he's carrying a gun most people would mount on a jet.
HOW: Use the containers. He can't see you around corners. Stinger missiles work; so do the remote-controlled missiles if you're good at steering them. My favorite way: set claymore mines in the paths he walks, then hide and let him walk into them. Never stand at the end of a long open row of containers. That's where he gets you.

09 METAL GEAR REX
The big one.
HOW: Stinger missiles again, aimed at the dish on its side (the radome). It fires missiles at you, so throw chaff to throw them off. In the second part of the fight the pilot is out in the open in the cockpit, and you aim at him instead. Keep moving, keep firing, chaff, ration, repeat. Something happens in the middle of this fight that I'm not going to spoil.

10 LIQUID
On top of what's left of Rex. A fistfight.
HOW: Same as the Ninja: punch-punch-kick, back off, repeat. Watch the edges, because you can get knocked off. After that comes a chase in jeeps through a tunnel, where you're on the machine gun. Shoot the driver of the jeep that's chasing you, and don't run out of life on the way. Then watch the ending. Then go read the spoiler page.