@DevoutSaucer13Best way is playing the Objective (PTFO), which means taking Flags in Conquest for example.
Byside that, focus on Spotting everything you see and giving Ammo(Support)/Health(Medic) if you play any of these classes.
• Best modes for much XP is basically "Conquest" and "Operations"!
Operations is awesome because if you'r Team is pretty good and you win, you'll get a big Bonus of XP for winning!
• And don't forget to activate a XP Boost, or join a Squad with one.
Ps: Watch out for BF1 double XP events, shows in the main Menu if active!