A few years ago, I stumbled on a copy of A History of the Hugo, Nebula and International Fantasy Awards by Donald Franson and Howard DeVore. It was published in 1978 by Misfit Press, and by "published", I mean this is actually mimeographed and bound with staples. It is wonderful.
It is also the gift that keeps on giving, especially when it comes to shining a light on the these awards' charming and chaotic early years.
The Hugo Award
The first Hugo Awards were given out at the Philadelphia World Science Fiction convention in 1953. From the first, the awards were decided by popular vote.
That said, the nomination procedure - and the definition of 'the populace' - changed from year to year. In 1961 the germ of the present system became codified in Hugo law, as the organisers of that year's convention still allowed for public nominations, but changed it so only convention attendees could vote on the final ballot. In 1963, this was changed futher - so that only members of the current or previous convention could nominate. This is largely the system we now have today. (Well, except in terms of governance - the new WSFS constitution came about in 1974 and changed the definitions of everything, although the theory is still the same.)
The number of prizes varied from year to year as the individual convention committees chose to add or subtract categories that they felt relevant. Other categories - such as Dramatic Presentation - came and went depending on interest.