Well my course (RR17) is only offered at ten universities (eleven including my nearest university, but I didn't particularly want to end up there although it's a lovely university. Stretch my wings 'n' all that): University of Bath, University of Bristol, University of Exeter, University of Glasgow, University of Leeds, The University of Manchester, The University of Nottingham, Queen Mary, University of London, The University of Sheffield and the University of St Andrews. Obviously all of these have a great reputation, so that didn't really factor into the decision making process.
I didn't fancy living in London at all, so that rules QM, UoL out at the first hurdle. Glasgow and St. Andrews are too far away and I would barely have been able to afford flights/the train at the start and end of term -- let alone have enough cash to pop back for the odd weekend! I was also rather averse to living in an industrial, northern/midlands city because that's too much like home (and I wanted a totally new experience, city-wise, although I did toy with Sheffield and Leeds).
So then I was down to Bristol, Bath and Exeter. I simply fell in love with Bristol on an all-expenses-paid residential visit to study German and Czech. The university, city, course, and department were exactly what I wanted (and how I had expected them to be). The last two failed to grab me in the same way and felt like smaller versions of the same sort of thing really.
So that's how I chose my university. Ultra-logically I suppose.