• Jump
  Press A. The longer you hold it down, the higher Mario will jump.
• Duck
  Press Down on the Control Pad. You can go down certain pipes by ducking while on top of them.
• Run
  Hold down the B button as you press Left or Right on the Control Pad to make Mario run. You cannot beat the game if you walk all the time! Also, if you're running and you press A to jump, Mario will jump higher and longer. Again, this is critical if you want to beat some of the harder stages; there are some gaps that are impossible to jump over if you don't take a running leap.
• Shoot fireballs
  Press B when you are Fiery Mario.
• Swim
  Press A to swim.
• Duck and slide
  While running, press and hold Down, B, and whatever direction you were walking on the Control Pad. Mario will duck and slide. This is useful for getting under narrow spaces.
• Moonwalk
  Duck and slide under some blocks, then stand up so that Mario is overlapping one or more blocks. The game will slide Mario to the right until he has cleared all the blocks.
• Climb Vines
  Touch a Vine and press Up on the Control Pad.
• Hidden 1-Up Mushrooms
  All the x-1 levels will have a hidden block containing a 1-Up Mushroom if you have warped to the level, or if you collected all the coins in the previous x-3 level. (The bonus 1-Up in World 2-1 only requires 21 of the 23 coins from World 1-3, however.)

World 1

1-1
Going down the fourth pipe leads to a secret coin room. When you come out of the secret room you'll be near the Flagpole. You can find an invisible block containing a 1-Up Mushroom if you go six block-lengths away from the fourth pipe and jump up. It is possible, although difficult, to get the 1-Up and still be able to go down the fourth pipe.

1-2
There is a 1-Up Mushroom over the last block on the right of the platform with 6 coins above it. If you're Super or Fiery Mario, quickly break the Block to the right of the 1-Up that just sprouted so the Mushroom drops down so you can collect it. If you're small Mario, not to worry -- just follow the 1-Up Mushroom and it will drop down over the pit with the elevator lifts. A well-timed jump can nab that 1-Up. However, if you were small and followed the 1-Up that far, you have passed the first pipe which leads to a secret coin room.
To find the Warp Zone in this stage, get on the second set of elevator lifts, ride it up a bit, then jump on top of the ceiling to the right. Continue to the right, and you will find the game's first Warp Zone! Here you can warp to Worlds 2, 3, or 4.

1-3
Your jumping skills will be put to the test here. Watch out for Koopas on the ground and in the air.

1-4
There are 6 hidden blocks containing 1 coin apiece hidden in the first wide-open area of this stage. Be wary of Bowser's fireballs!
To get past Bowser, jump over him or run under him when he jumps. Touch the axe and the bridge will retract, and Bowser will fall into the lava. You can also kill Bowser with 5 fireballs. If you kill him with fireballs, you'll get a cool 5,000 and you'll see that Bowser was really a Little Goomba.

World 2

2-1
The hidden 1-Up Mushroom is down in the area with the first Koopa Troopa. Go under the Bricks but stand one block left of them. Jump to find an Invisible Coin Block, then jump straight up off of that to reveal the hidden 1-Up.

2-2
The first water level. Fiery Mario makes this level a whole lot easier.

2-3
Keep moving, and keep an eye on the Cheep-Cheeps above you so you can dodge them easier. If you stand in one spot too long, a Cheep-Cheep will land on you. Remember that Cheep-Cheeps can be stomped on while they are out of the water!

2-4
Bowser is really a Koopa Troopa.

World 3

3-1
The hidden 1-Up Mushroom is above the bridge.

3-2

3-3

3-4
Bowser is really a Buzzy Beetle.

World 4

4-1
You will bypass most of the level if you go down the third pipe. The hidden 1-Up Mushroom is above the ninth ? Block.

4-2
There are two Warp Zones in this stage! Use the same technique as in 1-2 to find the warp to World 5. Finding the warp to Worlds 6, 7, or 8 is a bit trickier. After the first elevator lift, there is a pit and three Brick Blocks above you. There are four hidden coin blocks under the three Blocks above you, but the only two you need to hit are the ones under the second and third Brick Blocks. Jump on the stairs you just made and hit the first Brick Block to sprout a Vine. The Vine leads to the second Warp Zone.

4-3

4-4
This stage is a maze. The correct path is as follows: Take the upper route, go up the stairs, then take the bottom route.
Bowser is really a Spiny.

World 5

5-1
The hidden 1-Up Mushroom is in the gap between a three-block-high wall and two Brick Blocks.

5-2

5-3
Look familiar? This stage is the same as 1-3, except the lifts are smaller.

5-4
Look familiar? This stage is the same as 2-4, except there are more Fire Bars.
Bowser is really a Lakitu.

World 6

6-1

6-2
Directly above the sixth hill in the background there are 2 hidden coin blocks. Once you find one, jump on top of it and jump straight up to find the other one. Get on the second one and take out Lakitu, and you should be Lakitu-free the rest of the way.

6-3

6-4
Look familiar? This stage is the same as 1-4, except there are more Fire Bars. Yes, the hidden coins are in the exact same places.
Bowser is really a Bloober.

World 7

7-1
The hidden 1-Up Mushroom is above the second pipe.

7-2
Look familiar? This stage is the same as 2-2, except there are more enemies.

7-3
Look familiar? This stage is the same as 2-3, except there are Koopa Troopas.

7-4
This stage is a maze. The correct path is as follows: Bottom route, middle route, top route, take the top route over the fire bar. Then take the top, middle, then top again.
Bowser is really a Hammer Brother.

World 8

8-1
This stage is LONG, so keep running. Don't spend too much time killing enemies and/or collecting coins, or you may run out of time. Going down the fifth pipe leads to a secret coin room, but it doesn't really save you any time.
The hidden 1-Up Mushroom is between the second and third pipes.

8-2
Jumping straight up off the Springboard reveals a 1-Up Mushroom. Try to collect it, because you'll probably need a few extra tries to get through this tough stage.

8-3
This stage is arguably the hardest one in the game. Grab a Fire Flower if you can.

8-4
Another maze! The correct path is as follows: Go down the first pipe after the lava, go down the first pipe suspended in mid-air (there is an Invisible Coin Block to the left of it which makes a great stepping-stone), go down the first pipe after the lava, swim through the water, take out the Hammer Brother and continue to the right to find Bowser. Be careful! Going down wrong pipes will take you back to the beginning of the stage.
Bowser is really... Bowser!