The Hip area is one of the most crucial joint in the body. It is involved in a whole host of movements including flexion, extension, abduction, adduction and rotation. Look at performing numerous exercises that work the different muscles around the hip joint.
There are numerous exercises to develop the hip area, including squats and lunges. Whichever exercises you perform you should always follow the principals of good weight lifting.
As with any muscle, growth will depend upon a number of factors including the exercise you do, your diet, and appropriate rest.
Its easy to warm up the muscle around the hip joint, simply walking will create a natural lubricate and heat around the joint muscles.
Because the muscles around this area help with other exercise movements such as Squats / Lunges etc, its worth remembering that if you intend to work these muscles hard, then you should avoid performing other lower body exercises that require the hip joint muscles for stability.
Simple lying leg raises, can be performed at the end of the day or your workout to help tone up this area - focus on keeping the movement smooth and under control, rather than letting gravity bring your leg back towards the ground.