Start with the latest part drawing and make sure the revision is clearly marked. Include dimensions, tolerances, material grade, surface finish, and any machining allowances that affect the final part. If there are critical faces or sealing areas, highlight them so they are not missed during review.
It also helps to share the expected quantity, batch size, and annual demand. A foundry can then judge whether the tooling, process route, and inspection plan suit the job. For investment casting, this information often changes the way the part is quoted and produced.
If you have a sample part, photograph, or assembly reference, add that too. The more complete the enquiry, the easier it is to compare options and avoid back-and-forth during the first stage.