Shadow boxing at the start of session is very important to just basically loosen up anyway. What i do at the end of a training session, is pick up 0.75 kg hand weights, stand in your boxing position, and throw 2 sets of left rights, then 2 sets of left right left, then 2 sets of left, right, eft right (So basically 2 punches, then 3, then 4 and so on and so on. Then when i get to 10 i aim to do 10 sets. Then i put them down and work my ways back, from 10 to 2 with no weights. This helps bulid your shoulders and endurance, and then doing it with no weights gets you working on thats speed again and helps warm doen. Nice little exercise to finsh off with, and if doing in front of a mirror with a coach pushing you, then it usually gets u more motivated to do those final reps of 10. I now use 1.1kg weights.