Get through this world, and you can finally advance to World 7, where your ultimate enemy, Wart, is waiting for you! Birdo and Triclyde (or Mouser in), the mini-bosses of the pyramid, are guarding the finish line. It's not over! The worst is yet to come.
(1) Warp straight to map D! After climbing the ladder, you have a choice. You can skirt past most of this level by walking to the left after you climb up from the ladder. What you're standing in is quicksand, and you're sinking. Move to the left, and keep jumping as you do. You'll come through the wall and end up at a door. Enter here and you can go straight to map D. It might not be a bad idea to at least collect the first Mushroom before you take this route.
(2) Sub-space 1. In the grass on the right at the top of the ladder you'll find the potion. Take it, jump across the quicksand, and enter Sub-space on the second bone. There is a Mushroom on the cactus. Don't get careless and drop your Potion on the sand, or it will sink and vanish.
(3) Avoid Bob-ombs with a ladder. When you get to map B, Bob-ombs will come out of the jar one after another. You don't need to run away though. Just climb up the ladder and wait. The Bob-ombs will explode by themselves and destroy the jar.
(4) Call Starman! Lot's of Ninjis here! To be safe, don't blow up the wall as you ordinarily would. Instead, use the four cherries you grabbed along the way, destroy the lower wall, and grab the fifth cherry in order to summon Starman. Collect him as soon as you can, and take off!
(5) Sub-space 2. How do you get a Mushroom here? First, from the upper level, destroy the rock that stands in your way. Then go down the ladder to the lower level and break the wall. Then go up again, take the Potion, and come down. Give it a try.
At map C, climb the vines from the bottom all the way to the top. The only things that will help Mario here are the Mushroom Blocks. You may not see many enemies, but beware! If you fall down, you'll have to start all over again from the very beginning.
(6) Climbing hint 1: If you're not good at travelling sideways, you can go up by holding onto the vines on your right. But you'll have to go over three Hoopsters. It's up to you! Which is the worst evil.
(7) Climbing hint 2: Move sideways from vine to vine. Don't hesitate! You won't fall off if you're fast. You can make it by pressing up and to the right or to the left on the direction pad.
(8) Climbing hint 3: There are sniggering Snifits on the cloud. Carefully watch the height of their shots and get close to where they go by Mario's head. Go on up after the shots pass by.
In addition to those Snifits, you'll find a new cloud added to your ascent. On that cloud is a jar, and in the jar you'll find a potion. If you drop the potion right outside to create a door, and you'll find a third hidden mushroom in Sub-space. The extra health will definitely be helpful against the Mouser that you're about to face.
(9) Climbing hint 4: Climb up the vines on your left. If you go to the right where you see the three vines, you'll find three Hoopsters above you. So if you want to play it safe, go to the left.
(10) Warp back to map A. The warp door to the left of the starting point of map A brings you here. You'll have to face two mini-bosses, one after another, but you may want take this route and avoid maps B and C—they are very difficult! Unfortunately, you won't be able to increase Mario's life meter. Choose carefully.
(11) Fight without using blocks. Birdo is the first mini-boss. There's a Mushroom Block below you. You can jump on top of the Mask Gate and then jump through the green blocks above it to get to Birdo. Use eggs to defeat Birdo, but watch out for flames.
After defeating Birdo, grab the Crystal Ball and head through the hawkmouth gate.
Who's afraid of Triclyde? Triclyde is the second mini-boss. Check out those seven mushroom blocks on the floor. Remember that stunt you pulled in World 2-3? Build a wall by stacking three of them in a row. This way you'll be able to stay cool even though he's spitting flames. Now fling the blocks you have left at him. You need to bonk him three times.