I have heard this question so many times, so I figured if I am trying to help people start saving with coupons then this is definitely a question that must be answered. :)
Most of my coupons come from the Sunday newspaper. I bought the San Angelo newspaper for awhile, and I realized that I just wasn't getting coupons that so many of my friends from other states/cities seemed to be getting. I started getting the San Antonio newspaper, and it has seriously changed couponing for me. If you live in a smaller city, I would suggest buying a newspaper from a larger city. These can be found at gas stations, grocery stores, and other various places throughout town. These larger newspapers are more expensive (the San Antonio paper costs $3), but I ALWAYS make this money back many times over. There are three different types of inserts that come in the Sunday paper...SmartSource, RedPlum, and Proctor and Gamble. You don't get all of these inserts every week. In a typical week you get anywhere from two to three different inserts.
Another wonderful place to find coupons is on the internet. There are several sites that are devoted solely to coupons. Some of my favorite spots online to find coupons are:
www.target.com (this website has both Target coupons and manufacturer's coupons)
Each of these online sites lets you print two of each coupon. They also change out their coupons periodically, so it is always a good idea to check these sites often.
If I know that I am going to buy a specific product, and I do not have a coupon for it, I will often go to the company's website and see if I can find a coupon there. You would be surprised at the amount of websites that have coupons right there for the taking.
There are often coupons right at the stores as well. HEB is known for their yellow coupons placed right on the aisles in their stores. You can also find coupons placed on store shelves at Target, Wal-Mart, Albertsons, etc. Just open your eyes and start looking for them. Once you start searching, you'll be amazed at how many you'll find.