Depends on how you are retreating, if you are retreating pell-mell, keep the jab going with your chin down, and retreat at angles, stay away the ropes an corners, always looking for a chance to grab and hold. Grabbing and holding slows things down and gives you a chance to reset. Which looks worse, grabbing and holding or retreating around the ring pell-mell? They both look bad to the judges and fans, but holding allows you to reset and listen to what your corner is screaming.

If you are retreating in survival mode which means you have been hurt, anything goes. Fuck the ref, the judges and the fans, grab and hold if you can. Depending how bad things are, you might take a knee to listen to the screaming from your corner, and slow things down. Hey, don't forget the refs count.

If you are retreating one step at a time, due to your natural inclination or because your opponent insists on coming forward, keep the jab going, stay away from the ropes and corners, retreat at angles and circle away from his or her power. Who knows you might be that feared, badass counter puncher.

Stand up or hunched is a personal thing, in my opinion. Which one feels the most natural to you. Plenty of sparing will help you figure it out. There's probably nothing better than working privately with a good trainer.
I could say more but I have to scoot.