New to couponing and would love some tips.

I moved out of my parents house and now do all the shopping for me and my girlfriend. I live in Indiana and right now do my shopping at Walmart and am able to do 2 weeks of groceries for about 80$. I would love to start using coupons and get that price down. I don't know which sites I should use and I don't get the news paper so I don't have those coupons.