If you have money there are different laser treatments that help. Otherwise I've read that retinol can help. You can try inexpensive, over-the-counter types like ROC. If you use retinol, use once a day, apply at night and wear sunscreen during the day.
Frank coffee body scrub. Google it this stuff works magic on stretch marks and for me it helped so much with my cellulite. Check it out!
There are products made for this by herbalists who specialize in women's health. There's one called Belly Balm, but there are many out there. There are herbs that are used for this, as well as oils such as castor oil and jojoba, as mentioned above, and the products formulated for this combine things to make them stronger than just using one thing. If you have a good local health foods store they should have some of these products on the shelf, and consulting Prescription for Nutritional Healing and Prescription for Herbal Healing can be a good general resource. Look for materials from Janet Zand, an herbalist who specializes in women's health. Good luck.
I used jojoba oil for my scar. It takes time but it helped immensely.