Research with interviews, contextual inquiries and surveys to figure out where customer desire and business goals align
Using affinity mapping, personas & customer journeys to find where there are opportunities to meet needs and find pain points in the service.
Use low fidelity prototyping of interfaces and concepts to prove ideas, prioritise features cheaply and ensure developers are equiped to think in the customer's shoes.
Test and learn - find new opportunities, figure out what did not work last time. Nothing is perfect the first time around!