After the opening cutscene you take control of a fully powered up Kratos and will run through some basics of combat and movement taking on some Olympian chumps. After that a little Poseidon intro and it's back into the action. Gaia will blow out the fire and a few more chumps will come to get slaughtered. Then head over to the branches blocking the way and [R1] and then [O] repeatedly to lift them out of the way.
Boss: Stead Battle #1
You need to watch out for his high powered water breath. When the Steed rears his head use the R Stick to evade to one side. Then come back in for the attack. It doesn't take many hits to part 1 to be over.
Next you have to fight while hanging from the roof. Just get in close and be prepared to block when the Steed's pinchers come at you.
Then it's back to solid ground and this time you have to deal with the water breath and the pinchers. Keep up the pressure and you'll get to your first Context Attack. This one is a straight-forward [SQ] - [SQ] - [SQ] - [SQ].
Wall climb on the vines to the right and jump the gap. Climb up onto the solid ground and open the first Red Orb chest. These provide experience you use to level up your weapons. Continue on and shimmy around the rock face watching Gaia have a hard time of it as you go. You'll have to fight 3 basic enemies and 2 archers to move on. After they are dealt with climb the ladder to the vine up and deal with a few more basic low level guys. Grab the Green Health chest in the middle and then jump up to the right platform. Then Grapple over the middle to the left side. There is another group on the far side with 3 archers. Then jump to the ladder and continue your climb up.
When you reach the top Gaia will call out for help and the path in front of you will get destroyed. Double Jump over and continue to hold the jump button. This bring out your Icarus Wings and allows you to glide. You'll be double jumping and gliding A LOT in this game. Grab the Heath and Magic chest and then move on.
As you head through the next door you'll be attacked by a Centaur. When he charges Kratos, you'll get an opportunity to turn the attack back on the Centaur with a Context sweep of the left stick. Keep up the pressure making sure to block the Centaur's attack. A few other enemies will join in. This is a good first real battle and shows the importance of blocking in God of War III. Once you've done enough damage to the Centaur you'll get a Context attack to finish him off. Clean up the rest of the enemies and then pull the lever, climb the right ladder, and jump up on the platform to take it to the left. First save is up top here.
Back on to Gaia for another Steed battle.
Boss: Stead Battle #2
Mostly the same. Keep up the attack. A secret is to use your magic during a boss attack since it makes you invulnerable. You'll eventually get a Context attack to rip one of the pinchers off.
The next step will be a LOT of pincher attacks and the water breath will get a wider scope. Keep up the pressure until you get the Context Attack to rip open the Stead's chest and give him his pincher back.
Work your way through Gaia until you get to her heart.
Heart Of Gaia
GODLY POSSESION #1
First climb the right side to find "Zeus' Eagle".
Then climb back down and drag the right pillar to the center of the room. Rotate it 180 degrees and put it back in the left side. Now you can climb the left side and then Grapple to the higher point. At the top they will teach you about using enemies as a Battering Ram. This is a very effective technique in this game. Grabs in general are very good moves. Continue on and Grapple your way out of Gaia.
In the first section you need to eliminate the pinchers that are on each side of the battle. Switch sides when you see the ground start to spark with electricity. Also switch then the giant tentacles comes down. Once Gaia's hand comes down jump on it quickly.
Now you are fight Poseidon directly. Block and he brings down the Trident and then keep on him with attacks. Once you've done enough damage quickly climb the vines to the right to get a Context Attack on his head.
Back to eliminating the side pinchers. Watch for the electricity and attack with everything you've got.
Then you need to do a series of Grapple jumps and that will send you through Poseidon's form and take him with you to the ground. After a short conversation you'll get a Context Attack to finish him off. Now just watch the cutscene and you're on to the next Act.