The following was lifted from: https://www.gstatic.com/healthricherkp/pdf/autism.pdf
These won't all be applicable in every situation.
Behavioral: inappropriate social interaction, poor eye contact, compulsive behavior, impulsivity, repetitive movements, self-harm, or persistent repetition of words or actions
Developmental: learning disability or speech delay in a child
Cognitive: intense interest in a limited number of things or problem paying attention
Psychological: unaware of others' emotions or depression
Also common: anxiety, change in voice, sensitivity to sound, or tic