Given your number of topic posts, you should probably prepare twice as many as everyone else.
However, in one of my rare helpful moments, I'll try to give you an answer. Topics change from board to board, and if memory serves the essay is to be about 2 sides of A4 long.
The topic I answered on my main board was about the historian David Irving (he who denied the Holocaust), so it's obviously current-affairs based. As a result, you can't really prepare any essay, only practice writing them, so that'd be what I recommend, along with reading a quality broadsheet newspaper, and something like The Week.
The whole point of the essay, as far as I know, is not to test your current affairs knowledge, but rather to see if you can write in a coherent fashion, and get information across effectively, so practice doing that.
I guess you're still in school, so a potential idea would be to try and write an explanation of how something works, say, how a bike is propelled, then ask a teacher for advice on how to make it clearer and the passage information more effective. It works for some, might work for you.
Recently done my main board and not that i am going to give the game away but NONE of mine were on what you would exactly call current affairs i.e. stuff in the news.
Instead they were more abstract and about somewhat philisophical views of the world and people in general. Reading the papers is undoubtedly the best way to prepare but i would also say to try and ensure you are capable of constructing and arguement, clearly and concisely, no matter what the topic is.
You alright mate?
I did my main board 4-5 weeks ago and the topics we got were as follows;
-Obesity, should more be done to counteract it?
-Are leaders born or is leadership learnt?
I cant remember the others but they were along those lines anyway. Probabily the least challenging aspect of AOSB and everyone seemed to find it this way.
You then get debriefed on your essay performance by the education consultant the next day, if I remember correctly. He chewed me up for some poor grammar, and apparantly I wrote too much (1- 1.5 sides the requirement), although my structure and logic was fine.
The Leadership debate and whether or not you are born with it or it can be taught is a bit of a fave i believe. Either way, when given a bizarre title just make equal argument on both sides of the fence then wrap it up in a nice succint summary
As one who has marked essays at the board, bear in mind the following;
1. Good grammar and spelling count for a lot.
2. Learn how to use the apostrophe correctly.
3. Don't ramble-have an idea and express it clearly and concisely.
4. Make a plan on the page opposite-it helps.
5. See 1 and 2-especially 2