I use coupons.com mostly, but the main stores I go to either send a sales flyer, have the store's prices on the website, or both. My husband brings home the coupon inserts from the Sunday paper and I go through them and cut out only coupons for products that I would use anyway. I check the online coupons once or twice a week (or when they send an email about new coupons) and print them on the same basis--I would use them anyway.
When I make my grocery list, I write out the meals we're going to make (I only plan dinner since I'm working during the day, but make sure we have breakfast and lunch options for my husband and the kids). I don't get coupons for a lot of things, like meat or milk or eggs, because I buy the store's. Our main grocer does sometimes mail store coupons for their products, which I use.
Again, I check the website when I'm writing my shopping list with my coupons in front of me. I take granola bars to work for snacks and often have coupons for a few different kinds (like Kashi, Fiber One, Nature Valley, etc.). Whichever brand is on sale is usually the one I buy that trip with my coupon. My favorite recent coupon was for Edge shave gel, which was online, and I was able to print two. This past week it was for Edge or Skintimate and I printed two of that one. The coupon is for $0.75 off, my grocery store doubles them under $1, and the sale price at my store was $1.88. I got two shave gels for my husband and two for me for $0.38 each. (I don't make out that good most of the time--but I was super excited about that combination last week!)
If you price shop online before you go to the store, it also helps you to see the true price. Sometimes it is cheaper per ounce for me to buy crackers at the regular store rather than Sam's Club. I buy store brands whenever possible, but for the things we are brand-loyal to, or that are convenient, coupons are great. Another great deal I got lately was 20/$10 for Campbell's tomato or chicken noodle soup at Tops. I like tomato soup at work in the winter and had two coupons for $1 off 10 cans, so I got 20 cans for $8 and am set for my back-up meals for the winter. I agree that couponing is helpful but would never go to the extremes that some people do. Who needs ten years' worth of toothpaste, really? Planning your meals and only buying food you know you're going to use is just as helpful. I type out my lists by department, try to incorporate other things in the house that need to be used up, and build my meals around a bulk item when possible.
Sorry this is so long--nothing I have is really novel. :)