Play When There is Double XP
Occasionally, EA DICE will offer double experience events. These typically take place over the course of a weekend.
If one of these events is announced for Battlefield 1, make sure you take advantage of it. Double XP events are infrequent.
EA DICE will likely announce its plans ahead of time so you'd be wise to block off a chunk of time to play if you can manage.
Be on the lookout for an event sometime later this year, perhaps in and around the They Shall Not Pass DLC release in March.