Research the courses, check if they're suitable for your interests and learning style. Go to the open days and talk to current students and the academics (and check out colleges too), and ask them any question you have!
Also have a look at the course websites, as well as the prospectus and alternative prospectuses for individual colleges as well as the uni-wide one (which can be found at applytocambridge.com for Cambridge).
Anyone who cannot be confident of getting into at least one of his other four choices oughtn't to be applying to Oxbridge in the first instance. For anyone who can assume that, why not make the shot?
Hi, I'm considering oxbridge but have no idea where to start and I'm also not sure if it's even realistic, please be as harsh as possible I want to know if I have any realistic chance and if so where to even start? I would like to study history and politics at uni, I got 5 A*, 3 A and 2Bs and GCSE and I'm doing history geography and ethics and philosophy at A level, I'm predicted A A A but think I could maybe get and A*aswell if I push myself, I'm in year 12 at the moment, any advice would be much appreciated, please be truthful and realistic, thank you!
Oxford and Cambridge (and many other universities) often publish recommended reading lists for potential applicants or offer holders, I'd suggest having a look at some of the books on their list and seeing if you enjoy them (also, great to mention extra reading in your personal statement). You're in year 12 at the moment, so have a look at summer courses you could do (e.g. Sutton Trust summer schools, UNIQ summer schools, University of London taster days, some Oxbridge colleges also do summer programs, etc.) as these are a great way to try out studying the course at university level (as well as also being great personal statement fodder). Deadlines for these summer programs are rapidly approaching though - get on it ASAP.
On top of this, focus on really studying your subjects and gaining a more in depth understanding than absolutely required for you A level exams, think about doing an EPQ to explore a topic you particularly enjoy in more depth, and talk to your teachers for advice on how to push your grades up to an A*. Realistically, you need to be predicted as a MINIMUM the entrance requirements for the course (usually around A*AA) and many applicants will be predicted straight A*s (that's not to say you can't get in with *just* A*AA though).