BestBuy is offering Apple users in the United States 4 months of Apple Music for free, but its only for new subscribers. Simply follow this link, and you should be good to go.
A few things to keep in mind, firstly after the 4 months are up it will renew automatically. 2nd, in order to get the 4 months you still have to provide a payment method, although you will not get charged. And thirdly, if you are currently on an Apple Music plan or offer from Apple, this offer will not work with you.
Once you make the free purchase, you will receive a code via email to redeem on any of your Apple products.