Since moving to digital, it has helped with my spontaneity as I now load up the history from my last show at the venue and make sure I’m not repeating mixes. Beyond that, I rarely prepare sets in advance – although from what I read on sites such as this, I do get the sense that I may be in the minority with that.
As to what I pick next – it has to fit well with what is currently playing (be it a mix, a hard drop or whatever else I’m trying to pull off) and most of the time it will hopefully pump up the crowd more than the last track (unless I’m resetting, in which case it is something intentionally placed to recycle the floor a little).