Most children behave in more acceptable ways when they know what to expect. When they know what is to happen. When they can prepare themselves, inside themselves, for whatever is going to happen in the day, or at an appointment, or at a session, or at school. Some children become anxious when things change from the expected routine. Some adults are the same. Many children can be prepared for the day by talking to them and explaining in words. Many children need more. Some are really helped by visual material. The main thing about visual plans is that they can be referred to again and again, unlike words which disappear the moment they are spoken and have to be heard, understood and remembered from that brief moment.
Visual plans can be photos, drawings or symbols. Or even the real things/object representing real thing. At my sessions I use a visual plan for each child. Here is a sample. In this way the child knows what to expect, whether every task is going to be hard (I plan it so this doesn't happen) or whether there is something s/he really likes coming up. And there can be warning and acceptance about the difficult task, because there are also fun tasks in the plan. I ask the children to tick each activity when it is done.
Plans with objects, photos or printed symbolic pictures need preparation. Drawing can be done quickly and easily anywhere. And it really helps children. You can explain as you draw and they are then getting the language at the same time.