Pull ups until you can't do them anymore...use all the grips (neutral, supinated, and pronated grips). Joel Stubbs had the best back of all time to me and his back days consisted of pull ups, rows, and deads. Master the staple exercises
dont think of them as pulls,. think of them as pushes. pushing down with your elbows on vertical, or back on rows.
your hands are hooks and forearms are bars. i got more feeling when i started thinking of them like this, takes the arms out as much as possible.