If you're not good with remembering to bring your reusable bags to the grocery (or reusing old plastic bags), keep them in the trunk of your car! I used to forget mine all the time. We now keep two in each of our cars all the time, in case we forget or stop unexpectedly. When we bring them in and unload them, we leave them at the front door as a reminder to put them back in the trunk. It's a lot easier to use your own bags when you don't have to remember to grab them before you go!