Requirements differ by destination and by applicant. Use the official checklist for your route, then organise evidence by the question each item answers.
Identity and travel history
Keep a clear passport bio page, relevant previous passports and an accurate record of prior travel together.
Purpose and arrangements
Your proposed dates, accommodation and activities should agree across the form, itinerary and any reservations.
Finances and ties
Financial records should make the source of funds understandable. Employment, business and family evidence should accurately reflect your present circumstances.