I worked for several different large and small companies for the more than 5 years doing this same work. Now I work independently directly with customers to save them money.
The majority of my jobs are residential, in home maintenance, repairs, and assemblies. I also work with commercial businesses like gyms, apartments, and retail companies.
Gather some basic info about your equipment such as the model numbers, this will help the tech have a better idea on what to quote and how to better serve the customer. For an assembly make sure you've measured twice and have an idea or two for how you want things placed. It's usually much harder to move things around once they are built.