For those who use self-checkouts that are designed for full grocery carts - these usually have a scanning unit, then a belt that weighs your purchase and moves it down to the bagging area. Sometimes there is a divider in the bagging area that you can put in place that will divide your groceries from the next customer's. They let you bag yours after completing your purchase while the next customer can begin scanning. The store that I go to that has these is Meijer.
1. The scanner can be tricky - the unit must read the weight of the item when you place it on the belt, and sometimes it gets confused. And there is a lag time between scanning one item and the next. And sometimes they're just acting ornery that day. And then there is the issue where some people don't use these very often, so they get confused about how to use them. If you are behind someone who is having trouble with the scanner, please do not make comments or complain about how slow it's going. If you're in a rush, use a regular checkout with a checkout person, who can scan things much faster.
2. When someone has completed their purchase, it is up to them if they want to move their groceries down so they can put down the divider. It is not up to you, the next customer, to either demand that they put the divider down or for you to start moving groceries for them. I may have a lot of groceries and no, I may not want to pile them up on top of each other so you can begin scanning. And do not call the supervising person over to make me.
3. If the person in front of you has not put down the divider, or there isn't one, do not start scanning your purchases until they indicate you may do so. I scan bread last so it doesn't get squished. Sending your heavy milk cartons down when I'm not looking will probably squish my bread, and then I will be the one to call the supervising person over to hold things up for both of us while they go get me a new loaf of bread.
4. For self-checkouts that are for smaller orders, they are usually in clusters and there is a protocol that is usually store-specific for how the line operates. Observe this and proceed accordingly - in most stores a single line forms that feeds into the next available machine. But in some other stores, people line up behind the machine they want. Do not assume that every store operates the way that your favorite one does.
5. There is usually only one supervising person assigns to a large bank of scanners. This person must handle all issues for up to 10 scanners. If the person is helping someone else, be patient and catch their attention when they are finished, and be patient if they have another person in the queue ahead of you. Don't yell at them to demand they handle your problem NOW.
I love the self-scanners but hate some of the people who use them.