The conference will attract a "who's who" of industry giants.

No hyphens is correct, as you have it.

Hyphenate only if it was used in a construction like: His 12-of-13 shooting performance was a career best.

We likely would just call it a tuberculosis (it  isn’t used very much in the U.S. so we don’t encounter this). But we likely would use bacillus Calmette-Guerin if needed.

Yes, hyphenate that.

Yes, that's right.

Two commas: Bless you, Dr. Patel, for all you do.

I'd still argue that a comma would be wrong after 11 in that construction, since 320-pounder is essentially a noun modified by 6-foot-11. Since, indeed, you don't want the numbers to bump, make it 6-foot-11-inch ...

So, again, by far and away the best approach is to rewrite. That means 1) more clarity for readers and 2) less time unnecessarily spent on grammatical puzzles and 3) more time spent on endeavors contributing more to the greater good.

The cars need to be tuned up before the race.

As you might surmise, we could go back and forth and back and forth and back and forth on this one. In an AP story, we would simply rewrite to avoid this mess.

If it must be written, I would delete the comma after inch: The 6-foot, 11-inch 320-pounder ...

Or better:

The 6-foot-11-inch 320-pounder ...

And a happy summer to you!

Indeed, the previous answers were contradictory. I've deleted them.

Per Webster's New World College Dictionary, hyphenate as a compound modifier before a noun: black-and-white photography. But: The photo is in black and white.

 (blak´blak´ən) 

adj. 1 set down in writing or print 2 partly black and partly white [a black-and-white tie] 3 a) reproduced, rendered, etc. in black, white, and gray rather than in chromatic colors b) producing images in black, white, and gray 4 of, having to do with, or seen solely in terms of, polar opposites [a debater framing a complex issue in black-and-white terms] –n. 1 a black-and-white photograph 2 Informal a police patrol car 

[[with reference to black letters on white paper]]  1 writing or print [to put an agreement down in black and white]  2 a drawing or picture done in black and white 3 reproduction, as by photography or television, of images in black, white, and gray rather than in chromatic colors

Three-year retention period.

Those look fine.

This gets a little complicated and there's not a good answer. The best solution is to split the sentence into two. That's much easier on the reader.

The system will solve the problem of people asking, “Where can I find this?” But users need guidance beyond this, especially with a new system or user.

It should be spelled out. So it's best to rewrite to avoid having to start with a number.

No hyphen is needed in that construction.

No hyphens in any of that; they're not needed for clarity. In late July 66 million years ago, we had a picnic.

We use http://www ... to ensure that the link is clickable. If you're writing for an online audience, it could be wise to do the same. Typically, web addresses are written in all lowercase.

In AP style, it's lowercase.

I'd hyphenate that, yes.

For the answer to the "why," you'd have to ask Howard Angione what the thinking was back in 1977. Perhaps it wasn't a proper name then. At any rate, that style has been in existence for decades. Until now, it seems, no one questioned it!

Later today in Stylebook Online, we will change to Dow Jones Industrial Average. The change will also be in the 2019 print book. Thanks for asking!

We don't have a specific style for that. My preference would be to spell out volume (note the spelling). But certainly it's often abbreviated as you have it.

No. We don't hyphenate that construction using percent.

 The dash, the semicolon, the colon, the question mark and the exclamation point go within the quotation marks when they apply to the quoted matter only. They go outside when they apply to the whole sentence.

So, the question mark goes outside the quotation marks in this case. I'd also delete the period:

Who once remarked, “Work and play are words used to describe the same thing under differing conditions"?

Interesting question, and we don't have an established style for that. (That means there's no wrong answer!) I'm more inclined to use double quotation marks, for more clarity for readers. The idea of implied punctuation in the overall answer is probably a lot more obvious to us than to the average reader, who might be puzzled by single quote marks (which exist only to avoid having too many double quote marks). 

Indeed, it's off-puttingly and maddeningly inconsistent. But the English language is packed with such inconsistencies, sometimes for good or at least apparent reasons and other times just because of the way a certain word or phrase evolved in general usage.

My view on this one: If you were writing for a general audience that included readers in Florida, New York City and Minnesota (for example), I'd advise against mesatop because it could be off-puttingly unfamiliar and confusing and looks like some sort of isotope.

But for readers in Colorado, land of mountains and mesas, your reasoning makes sense. So you have at least my blessing, if that works. Enjoy your mountaintops and mesatops.