This comment makes me think you have never played starcraft.
Step 1: Hotkey units on 1-9
Step 2: Slam face on keyboard numpad
Holding down a hotkey to build things (even if you don't have the minerals) also increases your APM.
Lots of players (especially the pros) will spam actions in the quieter parts of the early game to keep their fingers warmed up, or to start building a unit the millisecond they have enough minerals to afford it.