The defence in a hook

 

In a defence for a hook, this is how your arm comes up to protect your face and the side of the head, near the ear. The defending arm is bent at the elbow. This is essential to protect the spot where your opponent is aiming. Also, from right here, you arm can safely spring back into guard position, plus  that arm can also immediately hit back, in an elbow punch! So, this is important to train with all the moves -- offence and defence -- in place, when you learn a particular punch. You must learn the offence, the defence plus the guard position (how to revert to it) and the footwork. 

Do not forget that the leg movement supporting a punch is just as important. Look at the feet placement in this defence -- the feet are straight, the rear foot on toes, to pass the power along the torso. That sort of feet-hand co-ordination may take a while to learn -- however you must practice all of them along, so that it becomes easier to do them in correct form. Initially you may learn to do each of these parts separately, but try to co-ordinate them all before getting excited about another punch:) Most beginners want to learn several punches. However it is even more important to learn all aspects of a punch and learn it completely before moving into a new punch: this way your ability to pick up fresh moves becomes far easier, believe me:)