Know the four functions of behavior to better understand your child.
It is important to understand that all behaviors occur for a reason. All human behaviors can be categorized into four functions. These four functions are escape, attention, access to tangibles, and sensory.
Note that these four behavior categories do not imply that these behaviors are "bad". These categories are labels for both positive and negative behavior actions.
An easy way to remember these four functions is that “Everybody EATS”.
Function #1: Escape
An individual engages in a behavior to end or avoid something they do not like.
Example #1: Every time Ms.Sam places a vocabulary worksheet on Stella’s desk, she rips up the paper and throws it on the floor. As a result, Ms.Sam does not make her do her vocabulary homework. In the future, Stella continues to engage in this behavior every time she receives a vocabulary worksheet because it results in escaping the vocabulary work.
Example #2: Kyla tantrums every time a demand is placed on her by her teacher Ms. Marie. Ms. Marie will ask Kyla to clean up her mess and Kyla will instantly engage in tantruming behaviors. The tantrum will go on until Ms. Marie decides that it would be easier to clean up the toys herself instead of going through the trouble of getting Kyla to do it. In the future, Kyla continues to engage in this behavior every time a demand (like cleaning up) is placed on her because it results in escaping from having to clean up.
Solutions & Suggestions If the individual you are working with is avoiding a demand or task some strategies that may be effective are:
Using a first-then board
Using a visual schedule
Establishing a good rapport o Using social stories TM
Follow through 
Function #2: Attention
An individual engages in a behavior to receive attention.
Example #1: Sarah screams every instance that her father walks away from her. When she engages in this screaming behavior, her father returns to her and asks, “What’s wrong Sarah?” This behavior is attention-maintained because the behavior consistently results in attention. When Sarah “wants” attention, she screams.
Example #2: Jordan licks the fence in the school yard when he is by himself. Every time Jordan licks the fence, his teacher walks over to him to tell him no. Jordan continues knowing that his teacher will come over to him again. This behavior is attention0maintained because the behavior consistently results in attention. When Jordan "wants" attention, he licks the fence.
(Please note that licking things can be a sensory component of having autism, in some situations it can also be an attention seeking behavior like in this case).
Other Examples: The following are examples of attention seeking behaviors in Autistic children:
Being way too loud, screaming, dancing, jumping
Asking for things way too often (If they are verbal)
Pretending they can not do something they are perfectly capable of doing
Acting violently, kicking, biting, or hitting siblings or other children.
Beating themselves, hitting his/her head on things, throwing themselves on the floor, pulling their hair, etc.
Solutions and Suggestions "If the individual you are working with has the intent to socially engage or get a reaction from another person some strategies that may be effective:"
Teach your child new and more appropriate ways to seek attention (e.g., tap on shoulder, “look at me”) and reinforce when these new behaviors occur
Give positive attention many times throughout the day
Ignore when undesired attention seeking behavior occurs
Function #3: Tangibles
An individual engages in a behavior to get access to an item or activity. A tangible is something an individual could touch or pick up. Individuals on the autism spectrum develop attachments to unusual objects like straws, rocks, scrap paper, pieces of dirt, flags, sticks, etc.
Example #1: When Jenna cries, her mother gives her a pacifier. In the future, Jenna cries because it consistently results in access to the pacifier.
Example #2: Joey wants a toy from his friend. During playtime, Joey will hits a peer which results in the peer dropping the toy and crying. As a result of the hit, Joey now has access to the toy he wanted. This hitting behavior will continue because he realizes when he hits a friend, more than likely he will then have access to the toy he wanted.
Solutions and Suggestions: "If the individual you are working with has an activity or item they want some strategies that may be effective:"
Increase the variety of activities/items your child is interested in so there are more things to help motivate your child
Teaching your child to accept ‘no’ o Control access to tangibles
Teach your child to request
Function #4: Sensory
An individual engages in a behavior because it physically feels good or relieves something that feels bad.
Example #1: Christopher engages in hand flapping in the absence of any specific antecedent or consequence stimulus. This behavior provides automatic sensory stimulation.
Example #2: Derek holds his ears when his peers are talking on the rug. This behavior provides automatically sensory stimulation as it reduces loud noises for Derek.
"Since the goal of sensory-seeking behaviors is to obtain some form of feedback from the environment, they can involve lots of different parts of the body. Sights, sounds, smells, tastes, textures, or body movements can all trigger sensory issues. Some examples include:"
Body movements (e.g., hand-flapping, covering the ears, hair twirling) Providing pressure or squeezing to certain parts of the body Waving or placing objects near the eyes Covering the eyes to avoid bright lights or patterns Chewing on objects or clothing Avoiding perfumes, lotions, or air fresheners Strong aversions to specific food textures. 
Solutions and Suggestions: "If your child has behaviors that are internally reinforcing that could provide a need for relief, a calming sensation, or a pleasing sensation, here are some strategies that may be effective:"
Introduce your child to self management techniques
Redirect inappropriate behaviors to more functional ones and reinforce those behaviors (e.g., tapping fingers on a table tapping keys on a piano)
Reinforce behaviors that are incompatible with the self stimulatory behavior (e.g. a child that flaps their hands would be reinforced for keeping their hands folded)
Physical exercise may decrease behavior
Seek medical advice