1. Members vote on works and people to be the official nominees in the various categories. A nominating ballot is sent out in January and each member is allowed to name up to five works or people in each category. At the end of the nominations period (typically in March or early April), the Hugo Administrator totals the votes and the top five eligible vote-getters in each category become the official nominees. Typically five hundred to a thousand members send in a nominations ballot.
2. A final ballot listing the nominees is sent out a few weeks later to the members of the Worldcon who have until about four weeks before the convention (which is usually held in the last few weeks of August or the first week September) to vote for the Hugo winners. The vote is carried out using a transferable preferential ballot and is counted by the Hugo Administrator. Typically about 1000 members submit a final ballot.
3. The results are kept completely secret until the Hugo Ceremony at the Worldcon when the winners are announced and the Hugo Trophies are presented. Following the ceremony, the detailed results from both the nominating and the final ballot are made public.
See Detailed Hugo Voting Process for more information.