The Lying Crossover Stretch Stretch will primarily stretch the Hip Abductor group (specifically the Gluteus Medius & Minimus).  This stretch also targets the Erector Spinae, as well as the Obliques.

The Standing Tensor Fasciae Latae Stretch will primarily focus on the Tensor Fasciae Latae which is commonly tight in runners and the general population.  Stretching this specific muscle can decrease the pain felt on the outside of the knee caused by excessive running (Iliotibial Band Syndrome).

The Modified Hurdler Stretch primarily targets the Hamstrings as well as the Gastrocnemius, and Erector Spinae.  You should be hinging from the hips and keeping the spine neutral oppose to leaning over with a rounded back.  This stretch should be incorporated in your daily stretching routine to help relieve excess tension in the Hamstrings and can be done in the comfort of your home, and requires no equipment

The Lying Quadricep Stretch is an alternative to the Standing Quadricep Stretch if you have problems keeping balance.  You can also stretch the Hip Flexors in this position by rotating the pelvis backwards to lengthen both Quadriceps and Hip Flexors.  The proper way of performing this stretch is to keep both sides of the hips in contact with the ground at all times.

The Standing Quadricep Stretch is probably the most common Quadricep stretch, and most effective.  To maximize the Quadricep stretch, and to get the Hip Flexors involved, tilt your pelvis backwards (bringing the belly button into your spine).  This stretch should be completed after an intense leg workout, followed by a Hip Flexor stretch to relieve excess tension.

This stretch is a very popular hamstring stretch that is very effective on releasing tension on the hamstrings.  Because it is one legged, you are more focused oppose to stretching both hamstrings at the same time.  It is very important that the hips do not lift up from the floor, so your main priority is keeping both sides of the hip in contact with the floor to efficiently stretch the hamstrings.

The Standing Hamstring Stretch is a very effective stretch when done correctly.  The most common mistake that people do is locking the knees (hyper extending) and putting unwanted pressure on the knee joint.  When stretching, be sure to hinge from the hip joint so all the tension is on the Hamstring oppose to the lower back.  Stretch to the point of tension, not pain!

This is the standard hamstring stretch that is used and highly recommended for tight hamstrings.  If you're suffering from tight hamstrings, the Seated Hamstring Stretch would be your best bet - but to successfully elongate the hamstrings, you need always remember to hinge from the hip, and not to let your back round in.