The wall slide is a good exercise to increase hip mobility and general posture. This exercise can be anhances with the use of an exercise ball.
Correct movement of the hip joint and lower back is also enhanced by this exercise.

The exercise:
Wall Slide start position
Starting position:

Stand with your back against a wall, using an exercise ball is better where it can be between the wall and your back.
Keep your back parallel to the wall, stomach tight so that your hips are in the forward or neutral position.
Your feet should be at about shoulder width and far enough from the wall so that your knees are never at an angle less than 90 degrees.

Movement:
Wall Slide finish position

Take a deep breath.
While exhaling, slowly lower yourself down the wall.
Concentrate on the correct pelvic alignment and be sure not to lower yourself so that your knees are past parallel to the floor. This action should be done at the rate of the entire exhalation.
Take another deep breath.
Maintaining the same posture raise youself back up the wall over the duration of the exhale.

Notes:

Be careful with the alignment of the knees, They should never go beyond 90 degrees, If any knee pain occurs stop this exercise.