To help the sage of the Forest Temple, you must first find the Forest Temple. To do this, refer to the "Ocarina Songs" summary and look under the "Minuet of Forest" section. This gives you an explanation of how to fund the Forest Temple. After you learn the song from Sheik, you will notice the entrance of the temple is elevated, and it seems that there is no way to reach it. Not so. There is a branch that reaches across the top of the opening. If you aim the hookshot at the branch, a red dot should appear (this means that what you are aiming at can be reached by the extending chain). Fire the hookshot and you will be pulled up to the branch and you should drop right in front of the entrance. Enter.
After you defeat the wolves, look around you. You will see a lot of crawling ivy growing on the walls. In some cases, you can hookshot onto the ivy (when the red dot appears, usually), as you can in this case. Climb up slowly to avoid the spiders and inspect the trees up there. You should find a small key. Now enter the main part of the temple. I will concentrate on the areas of this temple that have proven to be most problematic with players. There is a large, blue block that resembles the block in the Temple of Time. As you did in the Temple of Time, play the Song of Time to move this block and it will reveal a doorway. As you are exploring the temple, you will come across Stalfos Warriors - large, man-like skeletons.
I would recommend fighting these creatures in the same fashion that you fought those man-like dinosaurs in Dodongo's Cavern - with many jumping attacks. In this fashion, a lone Stalfos does not pose a real threat to your life. However, when you fight them in groups, you have to attack swiftly and with extreme prejudice. If you take too long in defeating them, the ones that were lying on the ground "dead" will arise once more and fight you again, possibly making the battle last forever if you are still slow in dispatching them. Another problematic room is the one with all of the paintings. You must have the bow and arrows to solve this puzzle.
Only fire at the painting with the funny-looking enemy in it. Repeat this until you have destroyed every painting. Then the enemy in the picture will emerge and you will have to fight it at the bottom of the stairs. I believe that you will fight two enemies like this. I find that it works best to Z-target them while you cannot see them, and then when they appear, fire an arrow at them. They will eventually die and the fire that consumes them will light a torch. There is another room with one painting hanging up. Study the painting and then fire an arrow at it. Blocks will fall from the ceiling and you will have to push them together in a fashion that resembles the painting on the wall. What is worse is that you only have a limited time to do this is in - so work quickly and carefully. After this puzzle is solved, you will fight an enemy that is akin to the previous one that I was discussing. Attack this enemy in the same fashion.
There is also the matter of the gray stones above doorways that appear to have a steel ring in them. These stones serve as holders for the hookshot, allowing you to swing across large gaps. There are also yellow diamond-shaped stones with an eyeball in the center. You will encounter these near the "twisted" corridors. When you fire an arrow into them, the corridors will be straightened out. It is in this fashion that you will be able to receive the Boss' Key (these are always in the golden treasure chests). The untwisting of the corridor will also flip the room with the Boss' Key around so that you can walk over to it and open it. There is another yellow diamond-shaped stone in the temple, but there is something strange about it - it is encased in ice. If you have the Din's Fire magic, this puzzle is easily solved - simply use the magic anywhere near the stone and it should melt. If you do not have Din's Fire, do not worry.
You can still melt the ice, but it is a little more difficult. You must jump onto one of the revolving platforms. You will notice that it is revolving around a torch. Fit an arrow to the bow, and try to line up the torch and the stone, and fire away. If you are a good shot, the arrow will pass through the torch, which will ignite the wooden arrow, and it will pass into the ice, melting the ice. Once you have gone through the temple and found nearly every treasure that is to be found, go back into the large room that was near the beginning of the temple. You will notice that three of the torches are lit. As you approach, a ghost will come out of the fourth torch and attack you. It is very similar to the last three ghosts that you have fought.
I would recommend a slightly different battle strategy, though. The real enemy will split into a few ghosts. As they circle about you, target each ghost quickly and fire the hookshot at them. If the hookshot strikes a ghost, it will disappear. Repeat this process until you strike the real enemy - it will flash and take damage when you hit it. It will then disappear and reappear with its fakes surrounding it again. Repeat this procedure until you have defeated it. When you have defeated it, an elevator will appear in the middle of the large room. You will take this elevator down to the lowest floor. There, you will have to push the blocks that kind of stick out of the wall (it appears that they have a kind of zipper in the corners). By doing this, you will make the entire room rotate - it will expose treasure chests and switches, the latter of which you should immediately step on when you get the opportunity. By doing this for a while, you should eventually open up the gate that was blocking you from entering the huge door with the huge keyhole in it (this is the door to the boss). Enter the door.
Walk into the room and stand still for a bit. A gate should shut you into the "art gallery" and a phantom of Ganondorf will appear on a horse. This enemy has two methods of attack. The first involves him riding into the pictures on the wall. You have to fit an arrow to your bow and keep turning around in circles until you find the painting in which Ganondorf is charging at you. Just as Ganondorf seems to emerge from the picture, fire an arrow at him. Repeat this procedure until you have unhorsed him. Now you will experience his second mode of attack. I find that the strategy which works best for me is to Z-target him. When he fires a ball of energy at you, time it so that you strike the energy ball with the Master Sword. It should reflect back at him. However, Ganondorf might knock it back at you. You must keep repeating this deadly game of catch until Ganondorf lets down his guard and the ball hits him. When this happens, Ganondorf will fall to the ground and attempt to recover. This is the only true time that he is vulnerable.
While he is doing this, attack him like you've never attacked anything before. He will probably become airborne again before you can kill him. Repeat this procedure until Ganondorf is defeated. You will earn a piece of heart and you will be transported to the Room of the Sages. Here you will find that the Forest Sage was an old friend of yours - Saria. She points you in the next direction of your quest - Death Mountain - and she entrusts the Forest Medallion to you. Your next adventure is covered in the next section, which is the Fire Temple section...
Proceed to Fire Temple...