Start with the purpose of the space: relaxation, play, entertaining, customer arrival, screening or easier maintenance. Note the areas that currently work and those you want to change.
Photographs of the site, approximate dimensions, location and information about water access make the first discussion more productive. Mention drainage problems, strong wind, pets, children and maintenance expectations.
You do not need a finished design before requesting a consultation. Clear priorities and honest constraints are more valuable at the beginning.