A loose guide; kind of in order:
Start with getting a sense of what they need the network to do. An eight person video editing team has drastically different requirements than an eight person sales team has different requirements from an eight person engineering team.
Then talk budget – this will likely be the largest constraint you’ll have to deal with.
Next up is gear. Mesh your expertise with what they think they’ll need.
Finally, look at the location. Don’t rely on a conversation – get photos and go see the place yourself.