i'd start my selection with the frame of the right geometry, weight and features such as threaded bottom bracket (i.e. non of the bb30, bb90, pf30, bbright etc nonsense), preferably external gear cables (brake cable can be internal as it almost never snaps), round seat tube without the braze-on tab, clearance for bigger tyres, no toe overlap, lively handling, mudguard and rack eyelets, hole in the fork crown as mentioned upthread, and of the colour that i like. i haven't found a frame that has all these features yet, perhaps custom is the way to go.