I agree with the suggestions to foam roll, and get ART if you can afford it. With the foam roller, do more than you think you should (30-40 passes per leg a few times a day). It is especially important to do it a lot in the beginning.
I have found a couple important stretches that can really help too, specifically with the piriformis, glutes, hip flexors, and hamstrings.
Pigeon Stretch- This is great for open up the hips. It will hurt at first if you haven't done it so go into it slowly.
Strike a Yoga Pose: Pigeon
Hip Flexor Stretch
Kneeling Hip Flexor Stretch
Hamstring Stretches- There are many ways to do these but just pick one. One thing I will say is that many people simply lean forward to touch their toes, but bend from the upper back. Consequently, they feel the stretch more in the back of the knee. Instead, really focus on benching forward from the waist and keeping your chest up, so you will feel the stretch in your hamstrings.
Standing Hamstring Stretch (Leg Stretches) @ ABC-of-Fitness
Piriformis Stretch- This is a bit repetitive after the pigeon stretch but I do them both. You can also do this stretch sitting in a chair, which is great for times when you are sitting for long periods of time.
Expert Back Care - Piriformis Stretch
Hope that helps some.