The percentages on BCSE are about this:
-Medicine (etiology, diagnosis and treatmentof disease and dentistry) - 25%
-Principles of surgery and antesthesia - 19%
-Diagnostics (techiniques and imaging) - 14%
-Pharmacology, physiology and toxicology - 14%
-Pathology - 13%
-Anatomy - 11%
-Preventive medicine - 10%
I just took BCSE and I was pretty confortable answering all the questions. What I can say about studying is like dvmjakish said: everyone has to find the way of studing that works for you. I used a variety of sources. What I suggest is first start on making a plan of study and follow it.
-Florida's lectures are pretty good, take notes about them, BUT do not rely just on what they talk about, they give a very very brief overview of SOME of the diseases, go further with large animals. The large animal internal medicine from the nacional veterinary medical series is really good and if you follow it, you will pretty much cover everything. But be aware that the book is from 1997 and the dianostic session is not accurate any more, so follow diagnostic procedures in Merck or somewhere else. And also, some of the "newer" diseases are not there, for example West Nile Dz. Keep in mind the common diseases (as dvmjakish suggested)
-Do not think that if you study superficially you will pass. You won't! So make sure that you know in depth every single common disease.
-I am totally small animal, so I didn't go over much of small animal. Study more the things you know the least.
-I studied a little bit of everything: even histology, physio, ... and what amazed me was the fact that even though there were just few questions about those topics on BCSE, it helped me relearn everything again and this was awesome even to answer clinic questions. It help you to think linearly and succeed in all qustions. That's because I think the big problem, at least in my country, is that we do not focus much on learning the basic subjects in vet school as they do here. And also as dvmjakish said: we all are vets and the more you know, the better you are. It is for our on good! So buy books and keep them coz they will help you in the future.
-In summary, I used nacional series for large animal medicine + merck for diagnosis, florida lectures, my own books, anesthesia I used the Oklahoma lectures, they are awesome:
http://instruction.cvhs.okstate.edu/vmed5412/ and the most important thing I did: I took notes of EVERYTHING and read those notes days after the test.
As you all know, we are not allowed to share specific questions, so here is my experience. I hope this help some of you and thanks for all of you that are sharing your experiences as well.
I will be happy to help anyone that still have any question about BCSE.