A personalized checklist, format specs, translation rules, and supporting letters.
One day late on a 90-day application timeline. Application rejected. You gather new statements, pay for another appointment, and wait another 6 weeks.
'Certified' means something very specific for each consulate. A sworn translator in Germany is different from a certified agency in the US. Wrong source = wasted money and a re-do.
Every consulate has a list of required content in supporting letters. Miss one mandatory element — like the host's exact address or relationship proof — and the letter gets discarded.
Notarization, apostille, authentication, legalization — these are not interchangeable. The wrong one means 2-6 weeks of rework. You learn this after submission.