Holding any button during the score tally screen completes it as fast as possible -- no need to mash!
Start, A, B, X, and Y can be used to select a new level during the overworld map transition.
Alternate mashing down + A to skip dialogue boxes as quickly as possible. Start slightly before the dialogue begins to have a chance at getting a frame-perfect quick skip.
Most level transitions (e.g. "1-1: Make Eggs, Throw Eggs") can be shortened by button mashing, which adds up to many seconds over the course of a run. The dpad and every button will work, so swirl the dpad and mash every button (including L and R).
Playing the Japanese version is estimated to save around 9 seconds in 100% and 7 seconds in Any% because of dialogue.
It was said that swapping to Hasty Controls in 1-3 hint box saves time compared to swapping at the stage selection. This was tested and the results are as follows:
Swapping to hasty at stage select takes 112 frames minimum and requires 9 inputs.
Swapping to hasty at the hint box in 1-3 takes 117 frames minimum and requires 2 inputs.
Tonguing walls is the quickest way to stop and turn around. When there is no wall available, holding down briefly is the next fastest way to come to a stop.
Running off a ledge causes yoshi to fall at max speed, thus the quickest way to fall down from an area is not to jump like in other games, but to simply run off the edge.
Jumping off of slopes as super baby mario gives him a speed boost. Also, facing the opposite way you want to move when jumping into a mario star gives you a speed boost (if you want to go left, face right as you jump into the star).
The quickest way to move up stairs is to walk along them for a split second, and then jump. Jumping too quickly results in yoshi's speed being much lower.
Jumping on both ice and snow is the fastest way to accelerate to full speed. Running on ice at full speed can make Yoshi run slightly faster than normal, whereas snow always slows you down.
Swallowing eggs or tonguing while fluttering should be done right as soon as the leg kicking animation starts, for they will not cause any slowdown there. The end of the flutter allows acceleration, which tonguing and making eggs cancel.
Ground pounding while travelling up towards doors may save time if you get an early stomp, which means you can enter the door during the ground pound animation. This is known as "Sex Stomp."
Hitting the bottom of the goal ring saves a small amount of time (1-10 frames) over hitting the middle or top of the ring. This is due to Mario being caught by the next Yoshi sooner. The difference between the very bottom and peak height of a jump is 10 frames.