Insta-Mine: While mining a block, move your cursor off stage while staying the same direction as you were. If you get good at this, you can mine forward while moving your cursor up and down to get more blocks and even mine faster than you can move sometimes.

Duplication: Astrauwu, the mod, was the first person to discover this. Place a chest, put an item in the bottom middle slot, name the chest, (using the n key) open inventory or crafting table, take the item, repeat.

(The old guide used a video for Insta-Mine)