https://www.jpmorgan.com/jpmpdf/1320747666950.pdf
If you do trials longer than 7 days you need to email the customer a week before he is rebilled with a direct link to cancel.
If you offer free trials / introduction offers you need to add the word 'trial' to the descriptor of the first monetary transaction after the trial.
There is also some extra stuff that needs to be added in the signup confirmation mail, like more details about when the rebill will place etc and a copy of the terms they agreed to