Hyphenated Names - What's the Protocol?

Factual Questions
1

When people marry and decide to combine their last names, is there a protocol for deciding whose name comes before the hyphen and whose after? Man’s first? Whichever sounds better? Coin flip?

Further down the line, what does the second generation do when John Smith-Jones marries Shirley Williams-Brown? Things could get awkward in a hurry.

2

I believe that’s all entirely up to the couple. If Smith marries Jones, either Smith or Jones can go first. Same with their kids when they get married - some will drop one of the names, or add to it, or simply use it as a middle name, and so on.