There are some basics I think one MUST learn, and the very first one is you must learn to copy ONLY in your head. Thats very important! From there you can begin to increase your copy speed. So copying in your head is a MUST. Jotting down notes or key words is fine to remind you of something you want to respond to during your QSO.

QSOing at 70 to 120 wpm is literally no different than having a conversation on the telephone; you are  just doing it using a different language! No sending call signs (except as required) and no sending bk. You dont do that on the telephone! Speaking on a telephone is operating duplex, therefore why not do the same thing on CW?