Be clear on the end result. Have a clear objective of what the 3d content should show, contain, demonstrate, or achieve. This will help you provide the studio/artist with a clear objective and hence what he/she needs to deliver.
Provide or develop a timeline. Provide or develop a timeline with clear due dates with input from the artist/studio. Keep in mind that at some point during the process, you will have to evaluate the work so the artist can modify it as necessary before the due date.
Work with artists that focus on meeting your needs. Aside from solid skills, talent, and experience, the artist should understand your needs. Artists that are focused on meeting your needs will listen carefully, ask a lot of questions, and provide suggestions on how to meet your objective.
Put it in writing. Have a contract that at a miminum includes the parties involved, the description of the work (including the objective and timeline), payment terms, rights and ownership.
If you are looking for custom work, contact us to discuss how we can meet your needs. At Flat Pyramid we have highly qualified artists that can deliver high quality custom work such as 3d model for your next project.