Use the A Button to perform standard attacks. By holding the Control Stick or Circle Pad in a direction and pressing the A Button, your fighter will perform a strong attack in that direction.
By quickly flicking the Control Stick or Circle Pad in a direction and simultaneously pressing the A Button, your fighter will perform a smash attack that can launch enemies into the air.
You can also control the direction in which you launch opponents. When you want to launch an enemy horizontally, flick to the side to unleash a side smash attack. When you want to launch an enemy vertically, flick up to perform an up smash attack.
The B Button is for special moves. There are four kinds: standard, up, side, and down--each determined by your input on the Control Stick or Circle Pad.
Pressing and holding the R Button will create a shield that protects you from attacks.
However, the shield grows smaller when it's deployed and is hit with attacks, and it'll eventually break apart. If a character's shield breaks, he or she will become temporarily dizzy and unable to move.
By flicking the Control Stick or Circle Pad while your shield is deployed, you'll dodge in the direction you flicked. When dodging, your fighter becomes invulnerable for a moment, so it's a good way to avoid enemy attacks...and you may even be able to get behind your opponent to counterattack.
Grab opponents by using the L Button or, when your shield is deployed, the A Button. You can then throw your opponent using the Control Stick or Circle Pad, or perform attacks on your captive foe using the A Button.
One of the secrets to winning is to maintain flexibility when fighting. For example, quickly grabbing an opponent after shielding against their attack or grabbing an opponent who is trying to block your attack are both good methods.