1a) Information
Pit always begins running with his right leg. This is to say he propels himself forward with his right leg, followed by his left taking the first 'step'.
His right foot, when it makes contact with the ground, produces a lower-pitched noise, whereas his left foot makes a higher pitched noise.
The above facts are true for any movement speed-walking, slow walking, or running.
1b) Applications
1) Up Smash
When performing a running up-smash, (sometimes called a H-smash), you may have noticed that Pit seems to slide a random distance. This sliding can encompass the attack itself or the charging of the up-smash. Sometimes Pit slides nowhere, where other times he can slide around 2.5 custom stage 'blocks'.
Upon investigation the sliding distance is far from random and is directly related to which foot Pit has on the ground.
If the up-smash is performed right after Pit's right foot makes contact with the ground (indicated by a lower 'foot' sound), you will maximize your sliding distance. As the frames go by further from that key moment right after his foot makes contact with the ground, the slide's distance shortens and shortens until his left foot makes contact with the ground. If the u-smash is used then, Pit does not slide at all, and will remain stationary for the duration of the attack.
Using this information, if you perform the up-smash as soon as the initial dash animation finishes, you will not slide, since Pit will be on his left foot. If you let him continue to run into his next pace, you will be able to consistently perform the maximum slide distance of Pit's H-Smash