Separate your zoom in and hold breath keys. Way better to zoom in then hold your breath when you want to seeing as you can’t hold it long.
If you’re going to standing from prone, just double tap X. Going prone to crouch to stand is just as fast as straight standing up, but it uses no stamina.
Use ACE Interact to switch your position in a vehicle without FFV slots.
Separate your items into different parts of your kit. I put my meds in my uniform, all non-expendables (my microdagr, map tools + light, etc) in my vest, and all ammunition from mags to grenades to rockets in my backpack.
If you have good timing, you can chain parkour with enhanced movement.