Well, what I would do will base on the assessment.
Stretching to muscle, joint capsules or ligaments if there is ROM deficit, of course, it depends on clients' severity.
Deep neck flexor muscle re-education would also be done.
Proprioception training to cervical spine (like to re-positioning) would be carried out if there is problem on such issue.
And lastly, general strengthening exercise would also be done toward later stage.
What do you think?