Become a regular visitor to Toad Houses
If you unlock five stars on your saved game file you'll then be able to repeatedly enter Toad houses, even ones you previously used that went inactive will be open for business again.

Coin Guide - 246 Star Coins in 53 minutes in New Super Mario Bros U

Another excellent video by GameXplain showing you where to get all 246 Star Coins in the quickest way possible.

Fireworks and bonus items at the end of levels
According to the numbers on the timer when you jump through the flagpole you can trigger bonus items and fireworks. If you jump through on 33 at the end of the timer you get 3 fireworks, if you jump through at 44 you get 4 fireworks etc. To get bonus items use these timings:-

- Fire Flower - timer should be on 33/44 as last numbers
- Ice Flower - timer should be on 55 as last numbers
- Star - timer should be on 88 or 99 as last numbers
- Super Acorn - timer should be on 77 as last numbers
- Super Mushroom - timer should be on 11 or 22 as last numbers
- Tiny Mushroom - timer should be on 66 as last numbers

Get star icons on your saved game; you have to complete a different task to get each different star added to your save profile
- Star 1: Beat the main storyline boss
- Star 2: Gather all the Star Coins in worlds 1-8
- Star 3: Complete all levels, and find all 94 exits in Worlds 1-8 then enter the Purple Toad Mushroom house.
- Star 4: Collect all Star coins from World 9.
- Star 5: Find and catch Nabbit in Worlds 1-7.

Get the ability to save the game at any time
Complete the story mode part of the game and the button labelled Quick Save will then become Save - you can then save the game from the overworld map at any time.

Penguin suit power-up
Once you've unlocked World 9 the Superstar Road go to one of the Toad Houses and you might just find this powerup waiting for you!

Propeller hat power-up
Once you've unlocked World 9 the Superstar Road go to one of the Toad Houses and you might just find this powerup waiting for you!

Purple Toad House
Complete the game in its entirety and you will be able to enter the Toad House in Sparkling Waters - here you can check out all the stats from the levels you've cleared, how many enemies you've killed what stages you cleared and how quickly etc.

Secret exit locations

Check out the above video by GameXplain which shows you all of the secret exit locations in New Super Mario Bros U (There are 12 in total)

Secret world shortcuts

This video shows you where to find all five secret world shortcuts again this video is courtesy of GameXplain. Shortcuts located in Acorn Plains, Layer Cake Desert, Sparkling Waters, Frosted Glacier and Soda Jungle.

Tiny Boost Boxes
The blocks in boost mode will be a lot smaller if you have 99 lives. When you lose a life they'll revert to normal size.

Unlock Acorn Plains level
Enter World 1-2 Tilted tunnel and locate the secret exit at the end of the level. There is a sloped purple crystal with a ring of red coins around it; Jump over the ring of red coins and you will find a hidden passage with some gold coins in it. While in the passage jump up at the top of the first slope and you'll come to a hidden passage made of square bricks. Continue along this passage and there's a hidden pipe. Exit the pipe and there's a red flag this is the secret exit that takes you to Acorn Plains.

Unlock Rock Candy mines level
Go to the Tower level and make sure you are Mini Mario (a mini mushroom is found at the start of this level). Make sure you are still Mini Mario when you are nearing the top of the tower and enter the miniature pipe you come to towards the top. The room you enter will contain Star Coin 3 and a pipe which leads to the secret exit revealing Rock Candy Mines.

Unlock Sparkling Waters level
Continue through the Ghost house as you would to go toward the normal exit. When you get to the room where nearly all of the walls are false (around the same location as the third star coin). Go to the middle of the room and you'll find the Boo near a signpost with some coins above you. Using wall jumps or the squirrel suit to reach the secret door which is in the air to the left of you as you stand in the middle of the room. When you go through this secret door it will open a room with lots of coins and a red pipe leading to the flagpole which is the secret exit and takes you to World 3: Sparkling Waters.

World 9 (Superstar Road)
Beat the game collecting all Star Coins between world 1 and 8 and you'll unlock Superstar Road (World 9)