Turn on Wi‑Fi and Bluetooth on both devices
Sign in to the same Apple ID on both iPhone and iPad (Settings → Apple ID)
Enable iCloud for apps you want to sync (Settings → Apple ID → iCloud → turn on the apps)
Turn on iCloud Photos (Settings → Apple ID → iCloud → Photos → Sync this iPhone/iPad)
Turn on iCloud Drive (Settings → Apple ID → iCloud → iCloud Drive)
Enable iCloud Keychain (Settings → Apple ID → iCloud → Keychain)
Enable Messages in iCloud (Settings → Apple ID → iCloud → Messages)
Enable FaceTime (Settings → FaceTime)
Enable Mail sync (Settings → Mail → Accounts → add/confirm the same account)
Turn on Contacts sync (Settings → Contacts → Accounts → ensure the same account is enabled)
Sync Calendars (Settings → Calendar → Accounts → ensure the same account is enabled)
Sync Reminders (Settings → Apple ID → iCloud → Reminders)
Sync Notes (Settings → Apple ID → iCloud → Notes)
Sync Safari (Settings → Apple ID → iCloud → Safari)
Sync Podcasts (Settings → Podcasts → enable sync if available)
Sync Apps via App Store (App Store → profile icon → Purchased/Family Sharing if used)
Sync music, books, and software purchases (Music/TV/Books apps → sign in with the same Apple ID)
Turn on automatic downloads (Settings → App Store → turn on Apps, App Updates, and/or Books/Updates)
Check AirDrop for quick transfers (Settings → General → AirDrop, set to Contacts Only)
Use Handoff (Settings → General → AirPlay & Handoff → turn on Handoff)
For backups, ensure iCloud Backup is enabled on both devices (Settings → Apple ID → iCloud → iCloud Backup → turn on)