Prepare your phone contacts to remote control your apps
1) Export contacts from your various accounts - this could serve as your backup should you make a mistake in cleaning contacts.
2) Turn off or pause any existing integrations in parallel (PieSync, Zapier, Fullcontact, etc). Leaving syncs on will interfere with cleaning in the next step!
3) Use the “find & merge duplicates” features of Google/iCloud/Outlook
- Instructions for Google Contacts
- Instructions for iCloud
- Instructions for Outlook.com
- Instructions for CRM, for example Pipedrive
4) Manually review your contacts and merge those duplicates that weren’t detected automatically, delete old contacts or old addresses.