put it down to a learning experience and try to improve as you progress, no ones an expert on the first try!
the best advise I can,t give is never shoot untill your personally sure you can make the first shot, mortal and 100% lethal
a 30/30 is certainly lethal if the shots placed correctly, but if you walk up on a deer thats down your not 100% certain is dead,
a shot to the neck is a good idea it wasted very little meat, and anchors the deer if theres any question of its running
