There is typically more than one way to design an interface, so I start by understanding desired features and trade-offs and generating several alternative designs.

These sketches help team members visualize possible design directions and select the most desirable one. These sketches can also be incorporated into customer research to understand which design direction will best meet users' needs.

Sketches are done quickly and iteratively and range from cocktail-napkin rough to wireframes. Here are some examples: example 1 and example 2