The first thing that I do with my golf clients is a go through a complete physical assessment.  Actually, I make sure their check cleared, then I do an assessment. 

The main reason for the assessment is to identify any physical limitations (weakness, imbalance, immobility, instability) that the client might have.  Once I identify the most glaring limitation, I try to "fix" it with corrective exercise and/or stretching.  By correcting physical limitations, I am hoping to prevent future injuries.  If the golfer plays through these limitations, they will most likely make compensations; compensations will cause microtrauma to muscles, tendons, and joints; micro-trauma will lead to injury over time.

Another reason to identify physical limitations with an assessment is that they can cause swing faults.  During the World Golf Fitness Summit this past March, Dr. Greg Rose and Dave Philips of the Titleist Performance Institute identified some common swing faults and their possible physical  limitations that can cause them.  I bolded possible because I don't want anyone to get the idea that I think the only cause of a swing fault is a physical limitation.  That's not what I am saying, it is just a possibility.  I'm sure there will be at least one idiot out there that misinterprets me.  I know there are plenty of uncoordinated, "motor morons" out there that refuse to take a lesson or go near a gym.  They can rot in swing fault hell.

As for the rest of you, I have listed some common swing faults and their possible physical limitations.

Faults are bolded, Possible Physical Limitations are Italicized

ADDRESS POSITION
C Posture (slumped over)
Weak Upper Back, Tight Chest, Poor Mid-Thoracic Mobility

S Posture (too much curve in lumbar spine)
Tight Hip Flexors, Weak Lower Abs, Weak Glutes

BACKSWING
Sway
Instability in Hip, Poor Internal Rotation of Right Hip

Loss of Spine Angle
Poor Trunk Flexibility, Shoulder Inflexibility, Lower Body Instability

Back Leg Straightens
Poor Hip Internal Rotation, Tight Illiotibial Band, Weakness in Glutes, Quads or Hip Abductors

Arm Collapse
Triceps Weakness, Poor Trunk Rotation, Lack of Shoulder Mobility

Poor Shoulder/Trunk Rotation
Trunk Immobility, Neck restrictions

Over Rotation
Lack of Core Stability/Strength, Instability or Hypermobility of Shoulders

DOWNSWING/FOLLOW THROUGH
Over the Top
Poor Core and Lower Body Stability

Hip Thrust/Early Extension
Poor Ability to Rotate, Lower Body Instability, Calf Inflexibility

Spin
Poor Lower Body Separation

Slide
Lack of Rotation, Lead Hip Instability, Lack of Internal Rotation in Lead Hip

Chicken Wing
Lack of External Rotation of Lead Arm