Reusable bags are a great way to help the environment. Returning your plastic bags to the store for recycling is a good idea too, however, it takes oil to make the bags in the first place, so it's a better goal to just stop using them altogether.
Most grocery stores sell reusable bags now, for a very reasonable price. I got lightweight canvas bags from Meijer for just $.99 a bag. Sometimes I hear an audible groan from the cashier, because they do take a bit longer to load, however, the stores prefer that you use them. It saves them money.
For a long time after I got the bags, I would forget to bring them with me. I started to keep them near me in the car, so they would catch my eye more easily, and now they've become a habit and I nearly always remember to bring them in. I use them not only for groceries, but for purchases I make at any kind of store. They're also handy for toting library books, packing for trips, etc.
I'm going to be gone on vacation for a bit over a week now. So I'll talk to you again when I return!