Really though, it may sound obvious, but knowing your controls is the first step to winning. "Super Smash Bros. Ultimate" has no shortage of control schemes and settings, so it's important to figure out which works best for you. While Smash veterans may prefer playing on the old-school GameCube controller (compatible with "Ultimate" via an adapter sold separately), the new Switch controls have a different layout and an extra button to customize.
In addition to the standard controls, pay attention to the "Other Settings" options. Lots of players prefer to turn off "Stick Jump" so they don't accidentally jump with the analog stick and die. Personally, I like to set my right analog to "Tilts" for quick attacks, and use Attack+Special for smash attacks. Some people like to set their Jump to a trigger button at the top of the controller for easier access.
Remember that Smash has two types of jumps: A regular jump that is performed by holding the jump button, and a short hop, which can be done by tapping the jump button. You should feel comfortable using all of your attacks at both heights.
Controls are saved to specific usernames, so you can set your personal preferences for different controllers and even create multiple names to use different control layouts for different characters.