First off, the title is misleading; feel free to improve upon it.
I've noticed words surrounding titles often start with upper case letters, but I'm uncertain if this is correct. After reading this article I cannot find rules that justify the uppercase letters.
EXAMPLES:
1) The student union building of many universities is abbreviated SUB but I often see the full name written as "Student Union Building". By itself "student union building" is not a proper noun since it doesn't refer to one unique entity but when speaking of a certain university it might.
2) Common buildings often have names beginning with upper case letters. For example, I've seen fire hall written as "Fire Hall" and city hall written as "City Hall" (example).
3) I have a ticket which reads "Winter Formal Dance".
Is the capitalization of these words correct? If so, then why? Is it a matter of rules, or is the deciding factor whatever the owner decides? For example, if a swimming coach decides practices on Wednesday will be known as "Wednesday Practices", would it be correct to always write 'practices' with the upper case "P"?
Best Answer
I love your question. :-) (very unprofessional of me, I know.)
Acronyms are always capitalized, in order to alert the reader that the nonsense word they have just encountered is, indeed, an acronym.
I think the pertinent concept here is titles. Though common words appear in titles, the words in titles are capitalized.
When buildings are given a (common) title (as in your example, Student Union Building), they are capitalized on the building itself (often in the school's literature as well), because that is the building's title. You need not capitalized when you write about them using the common name. One would be surprised to see "student cafeteria" on a building, because that is the building's title, and as such, the words should begin with upper case letters.
Pertaining to example 2, your source may provide you a semblance of an answer in rules 9 and 10. "City Hall" is capitalized because it is a specific city hall, Vancouver's city hall. It is a title (Vancouver City Hall) for a specific building. Random or unspecified city halls or fire houses are not capitalized. Same with specific town halls (Trenton Town Hall), hospitals (Good Samaritan Hospital), etc. They are titles.
Pertaining to example 3, specific events, like books, have titles, and the first letter of the words in a title (with exceptions you are probably familiar with) are capitalized. So while people run marathons, they might not qualify to run in the Boston City Marathon; your dance is 'titled' "Winter Formal Dance". Wednesday Practice is also a specific, titled event, even if it occurs every week.
You might look at this page. It has a bit more detail on the use of capitals than your source.