How is a First Officer chosen in Starfleet?
Does the Captain of a vessel choose outright, especially if it is a field promotion?
Does a Captain make a recommendation(s) to Starfleet Command, and Command decides?
Does Starfleet Command decide and execute these postings without input from the Captain under which the XO will serve?
In "Encounter at Farpoint", it seems Will Riker is assigned to NCC-1701-D without any input from her new captain:
"As for my crew, we are short in several key positions, most notably a first officer, but I'm informed that a highly experienced man, one Commander William Riker, will be waiting to join the ship at our Deneb IV destination."--Captain Jean-Luc Picard
In "Emissary", it seems Commander Benjamin Lafayette Sisko has some say in who will be posted, as he requested a Bajoran officer to be his XO.
What do you think?