Each child is quite individual and will have their own little character, however there are some hallmark behaviours which can be very common in children on the Autism spectrum. Some of these out of the ordinary behaviours can interfere with every day life, some may not; some be controllable while others are just part of your child.
- Lining up things. This can be quite common and often a child on the spectrum will revert to lining up their cars, blocks, trains etc instead of actually playing with them.
- Opening and closing doors
- Hand or arm flapping
- Spinning themselves or running in circles
- Counting objects for no real reason
- Switching lights on and off
Forming Lines
Often children on the spectrum can revert to forming lines when there perceive their environment as out of control. Creating a line formation can help them form visual order and may give them a sense of control in a dynamic situation.
Lines can be a way of coping with sensory overload that the child may be experiencing.
If your child uses lines as a way of coping, but at the same time can seem completely engrossed in the formation it can be a good idea to start diverting their attention to other activities that do not threaten their ability to create the line. Most line forming behaviour diminish as the child gets older and they learn to integrate their sensory overload, cope in dynamic environments and learn proper playing skills.
Routine
Children on the autism spectrum love their routines. It give them predictability and control. A slight change in a routine can escalate a child anxiety and provoke a meltdown causing a perfectly good day to go downhill. The good news is that flexibility in routine can be taught through specified therapies.
Flapping
Flapping can be seen as a child feels excitement. Often a child will be watching something of interest, or engaging in something they really like and may start moving their hands or arms in a repetitively fast movement. IT may also be seen while your child is engaged in physical activities. In this case the flapping is related to the activity and not necessarily excitement.
Other children may also flap when they are experiencing anxiety. As a child matures they may learn they flapping may not be socially appropriate and may then control there immediate need and go to a private place where they and flap.
Other Repetitive Behaviours
With autism can come other behaviours such as twirling, rocking, head banging, facial contortions, unusual voice patterns etc. The behaviours such as head banging, hitting them self in the face and facial contortions can be quite disturbing to parents as it is seen as an out of control behaviour.
Some parents and medical experts may revert to medication to try and control these behaviours. However another great way to handle these type of behaviours is to completely ignore them. Interrupting such behaviours can increase the child’s agitation which may lead to aggression. IT is tempting to want to stop these behaviours, but resisting the urge will be less stressful for both parents and child.
I hope this article helped you in some way. Please feel free to leave me your comment, I always appreciate your feedback 
Hundreds or research studies, done over the past decades show self injury is a hallmark trait of autism spectrum disorder. See blog article titled: “Self-injurious behavior in Autism Spectrum Disorder”