Momentum

Hit reg

The higher momentum (movement speed) you have, the higher chance you will have to get the first hit. When both players are clicking the same speed

(Assuming it's not 300 cps or something)

, the player with higher momentum will always get the first hit.

Knockback

Having more momentum also causes you to take less knockback. Similarly, having no momentum will result in you taking more knockback.

Methods

The most important thing to using momentum to your advantage is to not let yourself get slowed. This means jumping when possible, not walking into any blocks, and minimizing the amount of time you get slowed by when w tapping and blockhitting. Practicing parkour may help greatly with this. Also, placing blocks (bedwars pvp) or rodding

Using a fishing rod like in Uhc Pvp

can allow you to stop your opponent's momentum, allowing you to get the first hit.