Display Middle Name and Suffix fields in User Interface if you are going to need those fields - don't create your own.
- Definitely do this if you are doing legal contracts.

Fields

Rename Title to Position or Job Title to not confuse it with Mr, Mrs etc.
Rename all State/Province names to State
Rename all Zip/Postal names to Post Code
Rename Other Address to Physical Address to keep it similar to Accounts.
Rename City to Suburb

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Data Source - for where the record came from
Data Cleansing - for quickly marking any notes for bulk data fixes.
Preferred Name - especially when you need their full name for legal contractual reasons.
City State Country
Ultimate Parent
Campaign Monitor Fields

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Hide Birthdate or add it only to particular Record Types (Add fields for birth day and month is really needed. There should not be a reason to collect Birthdate - or maybe add it to the new Individual Object for GDPR Compliance).
Hide Assistant and Assistant Phone because if they are that important they should be separate contacts, and who really has assistants these days?
Add Do Not Call
Add Email Opt Out
Only include one address field - or lay out the address fields above one another rather than side by side because with State and Country Picklists as they are impossible to edit if you use the Edit button. (I haven't used State and Country Picklists in a while as I find them to be more of an issue than they are worth, but useful if you are still doing mailings).
Only have one Page Layout for Contacts unless you store a heap of data on Contacts!
Note, I always put Owner in the top right hand corner of the Page Layout, and Record Type in the top left. But if they are on the Highlights panel it may be superfluous. So you may put them in System Fields... but anyone that has moved from Classic can never find it in the Highlights panel

Views

Use a Salesforce Side Panel app in Gmail or Outlook - eg Cirrus Insight or Lightning for Outlook and Lightning for Gmail.

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