I work very closely with my clients and dive deep into their vision and plans for the project. I try to understand the goals like if I was the product manager for the application. If there is no detailed design I suggest some design templates that could serve as a starting point. During the development phase I usually use a Kanban-Board to track all tasks. I work very fast so there is no need for sprints or anything like that because the planning would take up too much time.
I keep my clients in a close loop and inform them about new versions of the app regularly, so they can start testing it early on.