For the past year, Starrett has posted daily mobility workouts on his MobilityWOD.com website, and the videos have become a viral sensation in the CrossFit community. Here he offers six exercises to increase mobility for specific sports—everything from running to climbing. Spend just two minutes a day on each move—the 10-minute squat requires more time, of course—and make sure to contract and relax in each position. Also, test your range of motion before and after: you should notice improvements almost immediately.

1. Posterior hip mobilization 
On all fours, position a stretching band around one quad, then place that foot in front of the opposite knee. Oscillate your hip against the band’s pull. GOOD FOR: Loosening up a stiff hip capsule or making you more efficient on a bike, in a kayak, or whenever you are in hip flexion.

2. Shoulder extension, external rotation
Place your hand through a stretching band and rotate your palm up. Grip the band and lean back,
stretching your arm above your head and engaging the lat muscle. GOOD FOR:  Opening up shoulder joints, which are particularly tight among swimmers and climbers.

3. Anterior hip mobilization
Place the stretching band around one quad’s hip crease and stretch that leg back, placing the knee on the
ground and slowly rotating the hip forward. GOOD FOR: Loosening up tight hip flexors, common among runners, cyclists, and rowers.

4. Ankle dorsiflexion
Standing up, place stretching band just above the ankle and step forward with that leg. Move knee forward and oscillate outward. Repeat facing the other direction. GOOD FOR: Ankle flexibility, which helps save runners tremendous energy.

 5. 10-minute deep-squat test
Stand with your feet shoulder width apart and lower your hips to your ankles, making sure to keep your feet flat on the ground. Remain in that position for 10 minutes, moving slightly to stimulate circulation. GOOD FOR: Increasing mobility in the ankles, knees, and hips.

 6. Couch stretch
Start on all fours with your feet against the wall. Raise one leg so the shin and foot lie flat against the wall,
then step the other leg forward, foot beneath you. Engage glutes, quads, and hip flexors by arching and relaxing your back. GOOD FOR: Opening up the entire anterior muscle chain, allowing you to fully extend your hips, knees, and ankles.

The ability to successfully perform a deep squat is a fairly good indicator of one's overall fitness level and movement quality. Is it the end all, be all?  Absolutely not, but it ranks right up there.

Squatting, for all practical purposes, is a complex movement that requires stability of the trunk and mobility of the extremities through constantly changing tension and position.

Moreover, the ability to perform a picture perfect (deep) squat pattern demonstrates that someone has proper ankle dorsiflexion, hip flexion, thoracic extension, and glute activation, which, as my good buddy and ass-Jedi Bret Contreras has noted, helps counteract or "undo" much of the musculosketetal issues we see in every day society: low back pain, anterior knee pain, hip pain,  hamstring strains, and groin strains, to name a few.

Lastly, the ability to perform a deep squat demonstrates one's obvious ninja-like qualities. But that goes without saying.

Yet some people just aren't ready to head to the gym on any given day and squat. They could have
really stiff ankles, poor hip mobility, poor core stability, or something more structural in nature like femoral acetabular impingement –  all of which can play a role in whether someone can squat to depth.

What follows are some simple strategies that we use at Cressey Performance on a daily basis to help
improve one's squat technique, and to a larger degree,  depth. Some are corrective in nature, while others are bit more specific to the squat itself.  Either way, I think many reading will walk away with some ammo they can instantly apply to their training.
Lets get to it!

But first, a brief reminder...

At the risk of preaching to the converted,  I can't emphasize enough that squatting deep is not dangerous for the knees.

A deep squat requires that the anterior surface of one's thigh drop below knee level on the descent. If one has the ability to go lower, great!  But I find the above criterium to be a fair starting point, and tends to be far lower  than what most trainees are used to in the first place.

Just to clarify, I'm not saying that everyone needs (or has) to squat "ass-to-grass." I'm not that na•ve nor pigheaded. The fact is, not everyone can (or should) squat below parallel without considering their training history, injury history, postural deficiencies, and/or mobility deficits.  I'd be remiss to state otherwise.  
 
Incidentally, what I find ironic is that most people (personal trainers included) think that squatting with a limited ROM is a safer way to squat. Epic fail.

Furthermore – and this should put the nail in the coffin – in a study titled Patellofemoral joint kinetics during squat in collegiate women athletes by Salem and Powers, it was shown that there was no discernible difference between three different squat depths (70, 90, and 110 degrees of knee flexion) with regards to patellofemoral joint reaction force and patellofemoral joint stress. (Clin Biomech  (Bristol, Avon), June 1, 2001; 16(5): 424-30)

In other words, and I'm just paraphrasing here, you're retarded if you go around telling people that squatting below parallel is bad for  their knees. Most likely, you just don't know how to teach it properly. 

So How Can I Squat Deeper?
Having said all that, the question then becomes, Tony, will you just tell me how I can squat deeper?

Well, as much as people aren't going to want to hear it, I'm going to say it anyway – how you prepare to squat is arguably one of the most important components that you can focus on.

Warm It Up!
Several common musculoskeletal issues tend to pop up repeatedly with many (if not  all) trainees I work with. These include, but aren't limited to:
1. Poor Ankle Mobility (specifically ankle dorsiflexion)
2. Poor Hip Mobility (specifically hip internal rotation deficits, short/stiff adductors and/or hip flexors)
3. Poor Thoracic Mobility
4. Lack of Core Stability

Read more: http://www.t-nation.com/free_online_article/most_recent/squat_like_you_mean_it_tips_for_a_deeper_squat