Check out the full guide produced by GoCardless here:
Chapter 1: Why move customers to Direct Debit?
Chapter 2: How to explain GoCardless to customers
Chapter 3: When and how to ask customers to switch to Direct Debit
Chapter 4: Different approaches to moving customers to Direct Debit
Chapter 5: What to say when asking a customer to pay by Direct Debit
Chapter 6: Dealing with objections
Chapter 7: What your customer sees when they pay through GoCardless