I worked at a grocery store back in Sugar Land, TX the year before I went AGR. Thanks to this experience I consider myself qualified to use the self-checkout aisles at grocery stores. Based on this qualification I have some advice for anyone choosing to use these wonders of technology.
If you have a full cart, use the regular checkout lanes. I know that you think you'll be able to get through quicker, but you're going to fail. Normally I'm happy enough to let you fail on your own, but your failure has now reduced the number of available self-checkout machines, which is going to slow everyone else down.
Don't go through the self-checkout if you have bought more than two bags worth of loose fruits and or vegetables. They don't scan and you don't know the 4-digit number to input. It is going to take you five minutes to look through the "identify by picture" menu on the register to find it. And that's assuming that you can tell the difference between the three different green peppers they have.
They have two different types of registers. There are the ones with the rotating bagging area which can keep like six different bags on the scales. There are also the ones which can only hold three. Do no take a cart with a bunch of items into the three bag area. You will run out of room, take off a bag to make room, and cause the machine to stop because it doesn't know you're a moron who couldn't see that the three bags weren't going to be enough space for your mammoth purchases. It thinks you might be trying to steal and it's trying to stop you from doing that. Wait for one of the larger bagging area machines to open up. You're doing yourself a favor.