User Research
Performing user research in order to understand the needs, attitudes and behaviors of users can be incredibly crucial in formulating a smart strategy and informing a smart design.
Card sorting, competitive review, heuristic analysis, clickable prototypes, focus groups, surveys, A/B testing, eye tracking - there definitely isn't a lack of options available. Some have more immediate value than others. For example, any kind of testing activity is always going to provide some sort of insight - but how do you know which test right for your project? As a UX professional I endeavor to keep abreast of all potential pursuits so I can speak to the need and validity in relation to the project at hand.