A few moms from social networking sites I am a part of, have asked me what symptoms I saw in my son, or what they should look for that may mean Autism. So here is a short discussion to help out, but please, even though I am not a genius in clinical psychology, feel free to ask me any questions.
The most blaring thing about our son was that he was still non verbal at 18 months. Completely. We thought it was his hearing (he had many ear infections), but he had tubes put in, his hearing was tested (perfect), and his ear, nose, throat doctor and pediatrician suggested we have him tested. We then realized he had other symptoms, sometimes as a parent you don't want to accept these things, or you turn a blind eye.
Here are some of his other issues:
little to no eye contact
not responding to his name 75% of time
huge tantrums for what seemed like no reason
repetivitve activity (stimming), flapping arms, filling and dumping buckets of toys for long periods
no empathy, reaction to our emotions
waking a lot during the night (has to do with sensory issues)
And later, here are some of his newer symptoms:
no pretend play
no playing with toys appropriately
echolalia (he repeats everything now that he is verbal)
inability to answer questions
That is just my son! There are many other symptoms that may or may not pertain to other kids on the spectrum. People discuss things like too many ear infections being a sign (which my son had). The biggest ones are being non verbal, and lack of social interaction: no eye contact, not responding, too much independence. So check some Autism sites for other things you may be concerned about. Most medical websites have some sort of checklist. But always ask your pediatrician!
Then go with your gut. Our first pediatrician would not accept his diagnosis so we went to 2 other developmental pediatricians with more expertise and they were a better fit for us.