Don’t use ampersands in body text or headers, unless they’re part of a company name, title, or other proper noun.
Exception: You can use ampersands to save space in charts, tables, and tweets.
The subjects joined by the ampersand must be related.
Note that ampersands might create issues for translation and localization.
Don’t use “+” to mean “and”, unless you’re referring to a partnership (like QuickBooks + Square).