Prepare PDFs for printing

I'm finalizing the print PDFs for the annual report that go to Henderson Press on Friday. Export the document so bleeds and trim are correct, convert spot colors to CMYK where required, embed all linked images, and include crop marks and a PDF/X-1a file for prepress. Before exporting, check for any objects set to overprint and report any missing fonts or low-resolution rasters so I can fix them.

Before I send the print-ready PDFs to our print vendor, make the file of the annual report easy for the press to accept: put the bleed, trim, and slug visibility up front, list any spot colors and whether they were converted to CMYK, show which images are below 300 ppi, and flag any overprints or transparencies that need flattener settings. Also surface the final page dimensions and intended paper stock so the press reviewer can approve at a glance.

I just opened the export dialog for the annual report and I see transparency flattening and overprint options but I don't know which settings Henderson Press expects. The art director and I are worried about white knockouts and trapped blacks. What is the most likely requirement from the press, what questions should I ask Henderson Press now, and which export settings should I use to avoid white halos or missing overprints?

Our print PDFs keep getting rejected for incorrect bleed, wrong color space, or embedded images at low resolution. Where am I repeatedly losing time and credibility with the press, and what three habits should I change now so future exports are right first time? Be specific about checkpoints before export and the quickest file checks I can run.