For basics of weapon handling
https://www.youtube.com/watch?v=NIM4WkHI8oU
http://iridar.net/planetside2/weapons/weapon-mechanics/

For recoil
https://www.youtube.com/watch?v=Nz-NPrDSaiA
http://iridar.net/planetside2/weapons/weapon-mechanics/ (again)

Headshots
https://www.youtube.com/watch?v=CZccuvkrB9I&t=312s

Cert farming
https://www.youtube.com/watch?v=aBdcYVCLy0U&t=633s