Doesn’t make eye contact (e.g. look at you when being fed).
Doesn't smile when smiled at.
Doesn't respond to his or her name or to the sound of a familiar voice.
Doesn’t follow objects visually.
Doesn't point or wave goodbye or use other gestures to communicate.
Doesn’t follow the gesture when you point things out.
Doesn’t make noises to get your attention.
Doesn’t initiate or respond to cuddling.
Doesn’t imitate your movements and facial expressions.
Doesn’t reach out to be picked up.
Doesn’t play with other people or share interest and enjoyment.
Doesn’t ask for help or make other basic requests.
By 6 months: No big smiles or other warm, joyful expressions.
By 9 months: No back-and-forth sharing of sounds, smiles, or other facial expressions.
By 12 months: Lack of response to name.
By 12 months: No babbling or “baby talk.”
By 12 months: No back-and-forth gestures, such as pointing, showing, reaching, or waving.
By 16 months: No spoken words.
By 24 months: No meaningful two-word phrases that don’t involve imitating or repeating.
(quoted from: http://www.helpguide.org/mental/autism_signs_symptoms.htm)