Ok ill just through in my two cents though Techie really hit it on the nail
Once youve got an area of debate just selectivly research it (thats why they invented indexs) but dont limit urself, in terms of distinguishing context other modern books are great (really historians are kinda bitchy) and USE UNI LECTURERES email them, there nice and will reply. Some even offer one on one help.
Gnerally when resarching i merely turned to teh hapter that had my debate in it and just read that ignorin the rest of teh book. It simply not needed. No piont in wasting my team reading a whole lot of irelvant things. Unless teh whole book focus' on your topic which is RARE but hey coudl be remarkably useful.
Even online texts can be dody from what ud figure was a reliable source as a freind found out this year at uni (used a harvard uni translation of a doc we were using in ancient to find it was translated incorrectly). Look at them for some general ideas but use books more or journals.
Journals are your friend, esp if u use them as a bench mark and resrach if the histprians put out a more extensive work. Some can be accessed at
www.library.usyd.edu.au
Id clear an entire day and do research, i did teh bulk of mine in two days at fisher library. Makes life easier then doin it one book at a time beacuse u can cross reference and follow ideas in one hit
Personally id suggest u find one big debate that gone on over a period (in my case portrayal of druids, another friend did "was pearl harbour known in aadvance", another did stonehenge "why was it built") and you can go from there a very strong focus will help you and make your essay more academic and consise
U MUST ACCOUNT FOR WHY THEY HAVE THIS OPINION, in teh words of my extension history teach "we dont want a history essay we want a historgaphy essay". It less about what there theories are and more about why they have them. This is quite fun and stands u in good stead for uni
look at past essays, mines on here and later ill post up some exempler essays that won prizes in previous years. These are a god send cos they give a very accurate idea when your writing how you should go about it. I did a source analysis of past exemplers and used that as a guideline to wirte my own
Oh and remeber footnbotes are you friend! if you odnt know how to wirte an essay go to
www.usyd.edu.au, click faculties, arts, school of philosophy and histprical thought, departments, history, course resources and there a guide you can dl and print!
BEST OF LUCK