What do you do before the meat of a weights session? Where does mobility work fit in? How much prehab work do most of you do?
General exercises to raise core temperatire, (e.g. BW squats & goodmornings, arm swings etc) then specific movement rehearsal with light weights. The total duration depends on the temperature and prior state of the athlete (Usually 10 -30 minutes). The warm up is not to be rushed, it can have a marked impact on the rest of the session. Most top lifters I have encountered perform an extensive, thorough wu (for evidence see Kolecki in Poilsh Ironmind)
Stretching, if needed, is done post workout.
I include prehab work at the beginning of the session for two reasons:
these exercises prevent injury and therefore are high priority; also if left to the end of the programme they are often not performed with the desired quality
the exercises may turn on stabilising or inhibited muscle which will be required to fire in the training that follows
During the competition season I include exercises for the scapular, hip and trunk for professional rugby union players.