labels - Are there guidelines for when to use UPPERCASE, Capitalize Each Word, or Only the first letter?

We currently use UPPERCASE headers and titles quite a bit (probably too much) and are looking to adopt a consistent set of rules for when it makes sense to use...

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  ALL UPPERCASE

  
  


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  Capitalize the first word

  
  



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  Capitalize Each Word.

  
  

I was hoping to find one simple generic rule that covers everything but haven't found it yet. I've found plenty of information regarding why I should never use uppercase ever because IT LOOKS TERRIBLE but that's not what this question is about.

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My question specifically revolves around text for things like:

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  labels "Sort by:" or "Sort By:"

  
  
  


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  tooltips "Primary address" or "Primary Address"

  
  


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  buttons "Delete user", "Delete User", or "DELETE USER"

  
  


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  navigation "HOME" or "Home"

  
  



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  breadcrumbs "HOME > MANAGE GROUPS", "Home > Manage Groups", "Home > Manage groups"

  
  

Answer

I researched the site with the most unique visitors to see if I could find a consistent pattern.

1. Facebook uses ALL UPPERCASE rarely in place of column header rectangles

2. Facebook capitalizes only the first letter of all the words in a field label

3. Facebook capitalizes the first letter of important words

In almost all cases where a full sentence isn't used Facebook uses the Titles of Works pattern -- Mark All as Read, News Feed Preferences, Log Out, Report a Problem, ...

Here is a summary of the general rules that Facebook appears to follow in most cases:

• Capitalize the first and the last word.


• Capitalize nouns, pronouns, adjectives, verbs, adverbs, and subordinate conjunctions.


• Lowercase articles (a, an, the), coordinating conjunctions (and, or), and prepositions (of, by, in).



• Lowercase the infinitive "to".

Source: The Chicago Manual of Style: 16 ed. paragraph 8.155 Titles of Works