Twitter DM?
EDIT: Direct Message. Doh!
Just saw this video from MKBHD where he, dbrand and OnePlus are giving away 100 OnePlus 3T phones, starting from 13 Dec (7 days from today). All you need to do is follow their Twitter accounts.
Twitter DM?
EDIT: Direct Message. Doh!
Winners will be notified by Twitter DM, so might want to watch that if you don't normally.
Also note that it's four phones/day.