This part will get you through the entire Fire Temple.
Inside the Temple
There's nothing we need to get outside the temple, so let's proceed inside.
Go straight north, breaking pots along the way that you may need to restore hearts with, and slaying the Fire Keese with your Whip, until you come across two locked doors on either side of a closed door. There are two passageways here: one going to the left and the other to the right. Take the one on the left first, heading north until you come into a room lined with spikes and having two rotating walls of fire. Sneak your way past the walls to the right and then up to the left, then take the passageway south until you come to a closed-door battle with some Stalfoses. Use your Whip to defeat them, causing the closed door to reopen and another door south of you to open. Go through that door into a room where you see electric sparks moving around. A stone tablet near the door tells you that the pitfalls in this room mirror the ones on the other side, so survey the room and mark the spots where they are mirrored in the room on the southeast corner of this floor. Make your way around the room to the staircase that leads up to Floor 2.
To your left, Zelda notes that there is a dilapidated old thing that was probably used as a vehicle. This is what we'll call a mine cart, so jump into it and it will take you for a ride to a platform where a small chest is located that contains a small key. Take the key with you as you ride the cart back to the staircase and down to Floor 1 again.
Go to the other staircase that drops off into the passageway north of you, but stop when you reach the top and use the Boomerang to hit the switch orb north of you. A sewer lid will drop down into the passageway. Go down and grab it, then take it with you into the passageway heading to the right, where there's a jet nozzle of some sort blocking your way, and throw the lid onto it. Jump onto the lid and then jump off it to the right. Continue to your right and you'll see a moveable block that you'll need to move to protect yourself from a flame-thrower to the right. Keep pushing it until you reach the passageway heading south, then enter the room that's a mirror of the one in the southwest corner -- except that you can't see the pitfalls here. Just remember where you marked them on the map and avoid them. There's a chest in this room that will give you 100 rupees. Head for the staircase that will take you back to Floor 2.
To your right there's another mine cart that we need to ride. Along the way, though, we need to strike two switch orbs in order to ride the cart all the way to a platform on the northwest corner of this floor. If you don't, the forks will lead you to other platforms where you'll need to ride the cart back to the one near the staircase to try again. Once you reach the one in the northwest corner, a Stalfos will rise to attack you. Strike it down with the Whip, then open the chest there which contains the small key and take it with you back to the staircase to Floor 1.
With the two small keys, open the two locked doors. Behind them there are two switch orbs you need to hit, either of which is timed. Use the Boomerang to hit the left switch orb first and then the right switch orb. The closed door will now open. Behind the door is the staircase going back up to Floor 2, which you need to take.
In the room that you re-enter Floor 2, the door will close, and a mini-boss creature called Heatoise will appear in the room with some electric sparks moving around the outer walls. Heatoise will mainly attack you by retreating into its shell and hurtling itself at you. Try to lure Heatoise into one of the electric sparks to stun it, then strike its head with the sword. Repeat this a few times until it is defeated. The closed door will now reopen, and a door to the right will open. Also a treasure chest will appear in the room that will give us our next useful item -- the Bow. You'll get 20 arrows with the bow and that will be all you can carry for now, but there are some places outside the Temple you can go to to increase that number.
Head through the door on the right and you'll see a staircase across a gap you need to get across. Fire an arrow at the red eye switch to the left of the staircase and a bridge will appear to cross the gap. Take the staircase down to Floor 1 again.
From the staircase, fire an arrow into the arrow redirect to the south of you. The arrow will go through another redirect into an eye switch to the right. A bridge will appear that will let you cross over to the platform where the arrow redirect is. Strike the redirect with your sword until it aims northward, then pick it up and throw it across the gap to your left so that it lands on the platform there. Then fire an arrow into the redirect so that it hits the eye switch to the north. A bridge will appear that will let you cross the gap to the platform. Go across, change the redirect's aim so that it's now aiming to the left, then throw it across the gap to the platform on the north. Fire an arrow into the redirect, and it will now cause the arrow to strike an eye switch to the left, causing another bridge to appear crossing the gap from the platform you're on to the left. Go across to the left and then head for the staircase that will take you down to Basement 1.
To the left is a locked door and a stone tablet next to it that gives you the most obvious of clues: "Remember, the only way to open this door is with a key." We'll come back to it when we get the key. For now, head for the staircase near the locked door that will take you down to Basement 2.
As soon as you enter this floor, you'll be in a closed-door battle with some Stalfoses that will throw their bones at you. Strike them down with arrows to defeat them. The closed door will reopen, and the door south of you will open. Replenish your arrows with the nut next to the staircase, then go through the south door until you see a post for whip-swinging on your right that's blocked by a flame jet. Aim an arrow at an arrow redirect to your left to hit an eye switch, causing the flame jets to shut down for a brief time. Then quickly whip-swing your way across three posts to your right. Head north, left, and then north while slaying the Stalfoses in your way until you see four sewer lids over some flame jets to your right. Time your jumps onto them when the flames are down, then let the one at center right and far right rise so you can leap onto the high platform on your right. Now whip-swing your way south until you are past the closed door and then press the floor button near the door to open it. Head to the left down a narrow passageway, being careful not to get hit by the flying bladed traps or to fall into the lava, then go south and then to the right where a small chest is located. Here we'll need to use the Boomerang to hit a Fire Keese first so that we can light up two torches with its flame. This will cause a sewer lid to fall onto an inactive nozzle to your left. Head toward that sewer lid, being careful not to get hit by the flying bladed trap, and use it to cross over to the staircase that goes back to Basement 1.
In the room that you reenter Basement 1, you'll have a closed-door battle with two Heatoises. Fortunately defeating them is easier: fire arrows at their heads to stop them dead. The closed door will reopen, and a door to your left will also open. A small chest will appear in this room, but it will not give you the small key. In this room there are four stone tablets which will tell you about the order in which to hit four eye switches that are above them. Make a note of that on your map before you go through the door on your left and take the staircase back down to Basement 2.
Head south and to the left, slaying the Stalfoses that are in your way, then head up and to the right where you'll see a floor button that will open a closed door to the left. However, stepping off it will cause it to close again. Behind that door is an eye switch we need to hit with an arrow, but first we need an arrow redirect. Go north until you come across one, pick it up, and take it with you to place near the door, making sure that it's aimed to the left. Then step on the floor button and fire an arrow into the redirect. When the arrow strikes the eye, it will cause a sewer lid to fall down. Pick it up and take it with you as you go back north, then drop it onto the nozzle to your left. Jump onto the nozzle when the flame is down and then ride it up one level to a platform where there's a pillar with two eye switches. There's also three inactive flame jet nozzles surrounding the pillar: one to the left, one to the south, and one to the right. There's also a switch orb near a closed door to the left, and an arrow redirect that points only in diagonals that we need to use in addition to the other redirect we just used.
Here's how to do this: get the diagonal-pointing redirect, place it over the nozzle on the south, and change its aim so that it's pointing to the northeast. Get the other arrow redirect, place it over of the nozzle to the right, and change its aim so that it's pointing to the left. Then get the sewer lid and place it on the nozzle to the left. Have Link stand on the sewer lid, then fire an arrow into the switch orb to cause the nozzles to activate their flames. Aim am arrow into the redirect that's on the nozzle to the south, so that it fires to the one on the nozzle to the right causing it hit the eye switch on the right. Then quickly fire an arrow into the eye switch on the left. The closed door will now open, and behind it is the chest that contains the small key.
Now to prevent ourselves from a lot of backtracking, go over to the switch orb on the right and hit it, causing a post to appear on the right that will let Link whip-swing over to the room where we fought the Stalfoses and to the staircase that heads back to Basement 1.
Use the small key to open the locked door, then head to the left and take a ride on a mine cart around some eye switches that we need to hit in the order shown by the stone tablets below. (The order is center left, far left, far right, center right.) If done correctly, the track will switch so that you'll get off at the platform in the center where the staircase leading to Basement 2 is located. (NOTE: If you run out of arrows doing this, use the switch orb to ride back to the northwest corner where you can replenish with a regenerating nut so you can keep trying.)
Just keep heading south to the staircase that will take you to Basement 3.
To the left there's a map of the mine cart rails with five marks on it that indicate where you'll need to hit switch orbs. Mark those locations on your map of the floor. To the right is a boulder that contains a sewer lid inside. To get the lid, we'll need to use a Bomb or a Bomb Flower (located across some islands you can leap over to on your left) to blow up the rock. Pick up the lid and place it on the nozzle to the right. Leap onto the lid so you can leap into the mine cart heading to the north end of this floor. Along the way strike the two switch orbs so you won't get derailed and get burned by a flame jet or lava. Next to where you get off is a stone tablet that tells you to carry the Big Key in a cart. Go over near where the Big Key is and use the Whirlwind to blow it onto a mine cart. Then leap into the mine cart just north of that to get yours and the Big Key's cart rolling. Now you'll need to strike the three remaining marked switch orbs to get the Big Key rolling all the way to the Big Key Door. (If it falls into the lava, you'll need to do the whole thing over again.) Pick up the Big Key where the mine cart lets you off and throw it into the lock to open the door. Then go through it down the staircase to Basement 4.
There's nothing we need to get there on this floor, just pots for breaking to restore hearts and weapons and a blue portal that will take you to the entrance of the Temple. Proceed to the staircase at the north and get ready to face the Temple Boss.
Temple Boss: Cragma
As Link enters the chamber, he sees a one-eyed stone gargantuan emerge from a pool of lava. This is the Temple's boss Cragma, whose most common forms of attack is to cause fiery rocks to rain down on Link and to occasionally pound the ground with his fists, both of which we need to avoid.
Cragma has bright spots appearing on his body, which are his weaknesses. When he first raises himself from the pool of lava, one bright spot will appear below his waistline. Strike that spot with an arrow, and Cragma will become angry and start his attacks. A giant rock will fall down, which contains a sewer lid inside: you can either use a Bomb to break open the rock to get it or wait for Cragma to pound his fist down toward the rock, the latter of which is rather risky. Once you get the sewer lid, take it with you over to where a mine cart is on your right and place it down on the flame nozzle so you can leap into the cart and start riding around, hitting other bright spots with your arrows. Cragma will try to reach out to you and grab you, crushing you for a bit before throwing you down to the ground where you'll have to get another sewer lid to get on board another mine cart. Hit the bright spots in his hands before he does. Once all the bright spots have been hit, aim for Cragma's eye. He will fall down, and the mine cart will take you back down to the ground where you can strike the bright spot on his head with the sword many times. Cragma will rise again and the bright spots will reemerge on his body. Again strike the bright spot below his waistline, then ride the mine cart around him and strike the bright spots that appear on his body. This time when aiming for the eye, make sure you hit it when it's open, because it will open and close. Again Cragma will fall down, and the bright spot on his head will be vulnerable. Get back down to the ground and strike it repeatedly with the sword. Cragma will go down for the count, indicating that you have defeated him. A Force Gem statue will appear, and so will a treasure chest that contains your next Heart Container.
You've completed the Fire Temple. Now step into the blue portal to return to the entrance.