Hit Selecting (Sumo)

Advanced Aiming
At the highest level, aim is just as important as cps in determining who will get the first hit. Aiming is more than just having your crosshair on your opponent.
Points of Aiming
Vertical - As mentioned previously, aiming parallel to the ground generally gives you the most reach. However, aiming near the neck or chest is more recommended because if you take vertical knockback, it can slightly throw your aim off resulting in you missing a hit.

Horizontal - Hitboxes in minecraft don't turn or rotate with the direction the player is facing. Since the hitboxes are rectangular prisms, this means the corners will stick out diagonally.

Prediction - Because ping causes a slight delay in positions and hits registering, if a player is strafing and you aim slightly in front of where they will be moving, sometimes you can get better hit reg.