Requirements: Kokiri Sword, Deku Shield, Deku Sticks
Hints
TREE-MENDOUS
You'll first enter the Deku Tree in the main room, which consists of several floors. The entrance is on the first floor. First of all, look around the perimeter of the room and climb a ladder or some vines. Now, follow the path along the circumference of the tree and you'll come to a large treasure chest, which contains the Map. You'll note that you can climb the wall behind the chest, but that comes later.
Keep going past this area until you come to a door. Enter the room and you'll have to knock out a Deku Scrub to proceed. Simply raise your Shield and knock the Scrub's Deku Nuts back at him. He'll bounce around a bit now, so quickly go to speak to him before he dives back into the hole again. You'll now be able to enter the next room.
In the next room, get to the other side either by jumping or by climbing up the vines. Open the chest to get the Slingshot. Now you must return to the main room; if the collapsing platform is still up you can use that as a (brief) stepping stone, but you can also Slingshot the ladder above the door to access the door. Now go back to the vines behind the Map's chest, knock out the Skullwalltulas, and climb to the top floor.
There is one door along this floor, which leads to the room containing the Compass. You'll have to step on the switch to lift the platforms, then quickly jump to the other side. Ignite the torch by using a Deku Stick to carry the flame from the lit torch to the unlit one, allowing you to escape from this room.
At the top floor, you must jump down and overstretch the cobwebs on the first floor in order to access the basement. I usually use a Jump Attack to break through the cobwebs and that works most of the time, unless you hit the side of the hole. The point is, you have to jump from above and overstrech the cobwebs in order to reach the first basement.
Don't worry about a hard landing to the basement, since you'll land in a deep pool of water. There are two dry platforms you can swim to, one which is guarded by a Deku Baba. Swim to the one without the Deku Baba and step on the switch to ignite a torch (and allow access to a chest). KO the Deku Baba, and behind him is a door blocked by cobwebs. Using a Deku Stick, carry some flame to the cobwebs (plot the route through shallow water beforehand) and burn the webs away to open the door.
In this room, send the Deku Scrub packing and use the Slingshot to activate the Eye Switch above the door. In the next room, you must dive underwater to activate the switch, lowering the water level enough to safely reach the other side of the room. You'll find the switch on the left side of the room, and you'll have enough time to activate it and wait for the moving platform to retract back.
In the next room, ignite the torches while avoiding the Deku Babas. In the large room which follows, you must ignite a Stick and burn away the cobwebs to access a crawlspace. Try not to go through the centre of this room, otherwise Gohma Larvae will jump down and attack.
After going through the crawlspace you'll be back to the first room you accessed in the basement, but now you'll be on the higher platform. Push the block towards the water, forming a ladder to the high platform from the rest of the room. Now, go back to the torch you ignited with a switch and use it to ignite a Stick. Carry the flame to the cobwebs covering the hole on the high platform, swinging the Stick with C to ignite them, and jump down the hole again.
Again, you'll land safely in a deep pool of water, which contains several Recovery Hearts. When you reach the door in this room, you'll find it guarded by three Deku Scrubs. Defeat them in the order of middle, right, left and the door will open. Go through the door and the long passage and you'll encounter....
QUEEN GOHMA: Parasitic Armoured Arachnid
Lock onto Queenie and ready the Slingshot. When her eye turns red, fire and she'll fall to the floor, stunned. Now attack repeatedly with the sword. It takes ten basic hits from the sword before Gohma falls, but you should only burn about two Seeds. If you need powerups, cut the grass at the edge of the battlefield. Wait a while and the grass will regenerate.
Once the Queen is down for good, get the Heart Container she leaves behind and step into the warp.