Start with the passport, purpose and place of residence
Write down which passport you will use, where you normally reside, the reason for the visit and the intended length of stay. Keep these together at the top of your preparation notes. They help you select the relevant official information before you request an employer letter, collect bank records or pay for assistance.
Describe the purpose accurately. A holiday, a visit to relatives, a business visit and paid work raise different application questions. If the trip combines activities and you cannot tell which instructions apply, put that uncertainty into a specific question for the responsible mission instead of choosing the shortest-looking checklist.
Keep the first version of the trip simple enough to describe: planned dates, places to stay and who will meet the travel costs. These are working notes for checking the application instructions. Make a separate list of reservations already held and decisions still open, so that an early itinerary draft does not become confused with a confirmed booking.