At an AGM or an EGM, only members of the society (ie those who have paid the membership fee) may vote. There will normally be a Returning Officer present, but for curiosity’s sake, the voting rules are as follows:

If a position is uncontested
You don’t need to have a vote, the Chair just needs to ask if there is any dissent (i.e. if any one has any problems with that person holding the position).
If two candidates are running for one position
You only need to have simple majority, this can be shown by a show of hands or by a secret ballot. Both candidates should leave the room while voting is occurring.
If there are more than two candidates
You need to use the single transferable vote.
Everyone voting should receive ballot paper and should rank the candidates in order of preference. There should also be the choice of voting for RON (Re-Open Nominations). The Returning Officer and another member of the society will then count the votes using the method as follows:
1. The first preferences are counted up. If one candidate has over 50% (exactly 50% is not valid) of valid ballots, then they win the election.
2. If no one has over 50% of first preferences, the candidate with the fewest votes is eliminated and their votes are redistributed (ie the second preference on the ballots where the eliminated candidate is first choice becomes the new first preference).
3. This continues until there is a clear winner

Quoracy
This pretentious Latin-sounding word simply means the number of members that need to be present at an AGM for it to be valid. This is calculated either as a fifth of the number of ordinary members of the society, or 10 ordinary members (whichever is greater).
If you do not have Quoracy
You can still hold the AGM but there are certain things that you must do afterwards in addition to the points below.
Email all the members of your society [this would usually be done by the Society’s outgoing secretary] and let them know this and the decisions made at the AGM within seven days.
Inform them that they have another seven days (from your email) to appeal to the Societies Committee if they disagree with anything that happened in the AGM, or if they disagree with the actions of the Returning Officer present.
For these 7 days the new committee do not take up office, the old committee will keep their positions.
We will let you know if we have received any complaints and if you need to re-hold your AGM. If after these 7 days no complaints or appeals are made then the AGM stands and it is treated normally. The new committee can then take up their positions.