I, like the poster above, made a spreadsheet with factors that I cared about (looking back, these appear to be... 'Percentage Satisfied with Teaching (UCAS)', 'Closeness', 'Area + Prettiness + Shizz', 'Intercalation Opportunity' and 'Extra Humanities Opportunities (i.e. languages)'...
Admittedly, I personally didn't go to any medical school open days so simply chose based on what scored highly/which unis I liked/ensuring I didn't apply to more than 2 BMAT unis.