Start with thank you's for the venue and to all that have attended.
Does your charity have a constitution, you may wish to find out and make sure you adhere to it during the meeting. Some AGM's read them out but you may find people asleep by the end.
Think about what has happened through the year, various events, fundraisers, thank people but not individually as you end up offending someone as you have forgotten them. Mention what a good year you had and that you are really hoping this next year will be even better.
Thank everyone who is retiring from the committee for all their hard work and effort.
You then need to elect your committee for the following year. Chairman, secretary etc. You someone to offer themselves for the position and someone to 'second' them in.
You may wish to break for refreshments in the middle. Some AGM's have a speaker to talk about their own subject for 10-20 minutes or so. Depends if you can find someone relevant to your charity.
Arrange the next meeting. Thank whoever made refreshments and thank everyone for coming
You need someone to take minutes of what was said, who was voted for each job, what time the meeting ended, date, venue.
Hope this is helpful. Try and get hold of the minutes for last years AGM, this should help too.