How would one achieve a tight, sharp Jawline and Chin? (photos)

To  tighten the neck and jawline requires a neck lift which involves removal of fatty deposits above and below the platysma muscle in the neck and a platysma plasty. When patients are over 50 years of age, then a lower face and neck lift will need to be performed due to inelastic skin in the neck that needs to be tightened. If patient's have a weak chin profile, then a chin implant can be inserted at the same time for better facial balance and proportions. For many examples, please see the link and video below

To restructure a jaw and neck angle depends on what the patient has to start with.  Generally speaking, chin implants, under chin liposuction and/ or radiofrequency ablation, platysmal release, mini-lifts, Thermage and other modalities could all be considered depending on one's anatomy.  Seek out a consult with a board-certified surgeon.  Best wishes.