Cy the tip guy says:
DOUBLE XP IS NOW LIVE FOR THE REST OF THE WEEK! to maximize your XP earns, follow these simple tips! For multiplayer: play longer lasting modes and do challenges! Earning calling cards and prestiging your weapons earns you TONS of bonus XP! For blackout: play “Pandemic”! There are so many merits to be earned when you can get 40 or more kills! For zombies: do gauntlets and complete challenges! Gauntlet medals give you a lot of XP you can use! Enjoy the grind community!