I'm always acutely aware of the need to vacate the runway in our very busy, full ATC, environment. Sometimes after landing, ATC does not have a spare second to talk to me and I am left wondering what to do. I have in the past taken an apparently vacant taxiway without being asked and then stopped past the hold-short line waiting for instructions. No-one complained, but I don't know if that was the right thing to do; I certainly don't want to stop on the runway. A couple of times, after missing the 1st exit I have found myself hesitating at the intersection with the crossing runway, obviously I cannot backtrack on that without permission, but it's a much faster way to get clear, than trundling another 2500' to the last taxiway, so I have paused. So far they have always told me to backtrack. I suppose if they didn't I would have no choice but to taxi as fast as possible all the way to the end.