Once a week Old Navy releases coupons on their website HERE. They hide them throughout this website. (NOT their regular website!) You wont know when they release them, but you will know the day. Its today! So keep your eye on this website, then when the coupons come up click around like mad to find the good coupons! You can only have one, so make it count! There will be some $75 off $100 purchases to be found! Those are the best ones, so look for those, they go fast!
Also, Thrifty Northwest Mom has some more great information on her blog HERE. She also does a chat room, so that when the site goes "live" you can have help finding the coupons!