Hugo editor voting works like every Hugo category. Voters nominate their favorite people or works. The top five vote-getters make it to the final ballot. If nobody wins a majority in the first round, the Hugos use the Australian ballot form of instant runoff.
Fans find out who edited a book or magazine by looking inside. Magazines usually name their editor inside, on the masthead. In recent years SF book publishers have started following suit. If you read the copyright page of an SF novel from a major US publisher within the past five years or so, the odds are very high that there will be an editor listed.
As far as evaluating the quality of an editor's work, Hugo voters use the same criteria as voters for other awards in the arts:
- What did their expert knowledge tell them?
- Did the disparate creative elements recombine into a gestalt that changes their thinking about art and life and love and cheeseburgers?
- Even if they have no idea how the nominee contributed to the work, did they have fun?
- Did they enjoy elements of the work: Did it have enough witty dialog, or passionate kisses, or shiny explosions?
- Have they enjoyed other works by the same artist?
- Did their barber/hair stylist like it?
- What did the nominee's co-creators say about the nominee's contribution?
The Hugo editor categories have an interesting history. When the Hugos first started there was a "Best Professional Magazine" award. Editors were mentioned in the award citations (and were given the trophies, IIRC). But it made more sense to have the award be for a magazine rather than an editor, because magazines were more consistent. An editor might leave a magazine for any number of reasons (to write, to edit in a different genre, or even to leave publishing), while a magazine would often keep much of its individual style even as its editors changed.
Besides, magazines were the heart and soul of the field. Here are some stats about Hugo awards and SF magazines:
- The 1957 Hugos were given only to periodicals.
- All of the short fiction winners before 1968 were first published in magazines.
- Most of the short fiction nominees were, too. Only one nominee in the first 10 years was first published in a book. And only a few others before 1968.
- Most of the "Best Novel" winners (and nominees!) before 1968 were first serialized in magazines. A lot of of the others were either excerpted in magazines or were expanded from shorter works first published in magazines.
So, magazines dominated the field for a long time. But what happened in 1968? (And wasn't the question about editors?)
A couple of things happened, one slow, and one dramatic. First, the SF field grew, and most of the growth was in books. Second, in 1967, BOOM!: Harlan Ellison's anthology Dangerous Visions was published -- and it dominated the 1968 Hugos. Most of the short fiction nominees were either edited by Ellison or written by him, and so were most of the winners. There was no "Best Editor" award for Ellison to win, so the Hugo committee gave him a special award. In 1972 Ellison got another special award for editing the followup, Again, Dangerous Visions. In 1973 Hugo voters finally saw the light and replaced the "Professional Magazine" category with "Professional Editor" (To be fair, a Hugo rule change takes years -- the process is deliberately slow.).
Hugo voters seemed to read the new category as "Professional Magazine Editor". First, because voters often didn't know who edited novels. Second, because few anthologies have the impact of Dangerous Visions. Third, voters would see a magazine editor's name every month. So, no book editors won for the first twelve years. Then book editors won three years running -- editors who were influential, beloved, and (usually) dead (1985: Neuromancer's front cover said "Edited by Terry Carr;" 1986: Judy Lynn Del Rey, one of the namesakes of Del Rey Books, died; 1987: Terry Carr died.). Then came a long stretch of wins by Gardner Dozois (editor of Asimov's Science Fiction magazine and a series of massive year's-best anthologies), occasionaly interrupted by other short-fiction editors.
Since SF novels are talked about more than short fiction (and get a lot more Hugo votes), it seemed unfair that novel editors weren't getting any awards. There were two responses. Some fans lobbied to split the category. In 2007, "Professional Editor" was replaced with "Editor, Short Form" and "Editor, Long Form." And book publishers started routinely crediting editors on copyright pages, just as they had been crediting cover artists for decades.