Delayed speech, hand flapping, hitting himself, very poor eye contact, pacing back and forth, screaming constantly, the EEEEEE thing, he still does that too, lol. As soon as we realized something was very wrong the school system came in to help us figure it out, we then got him diagnosed by a shrink. there are many signs and they all vary according to the child, but those were just some of my sons. good luck to you!!