I am currently getting rid of my teen stretchmarks, I, unfortunatly have horizontal ones from growing to tall to fast, and vertical ones from getting put on corticosteriods when I was 15 (They destroy collegen, among other things) and gaining weight.
Here is was is working REALLY good for me. Go to a store, pick up St. Ives medicated Apricot scrub (You don't NEED St Ives but its 3 bucks and I think its much better), a pair of exfoliant gloves (Look in the womens cosmetics section...and expect some stares.)And Palmers for Stretchmarks, Or Palmers with coca butter and Vit E. If you can't find either (Palmers brand is regarded as best by most people) Make sure you read the ingredients and that coco butter is in the first one listed, unfortunatly just like bread makers calling caramel dyed white bread wheat bread, some lotion makers make the coco butter claim with it being a minor ingredient.
Apply Apricot scrub and use your exfoliant glove on the general area of the stretch marks, dry very well with a towel and apply your coco butter/vit E lotion.
Personally I exfoliate very very rough twice a week and gently every other night and I am seeing GREAT results. From what I have picked up from a ton of reading is that your going to need to take off a whole lot of skin and when your body re-generates it, hopefully it will do so without the marks. I have seen some of the shallow ones go completely already, im sure the deeper ones will take more time but I couldn't be happier!