Lack of eye contact, or little eye contact. This is not the same as evasive behaviour.
Monotone intonation of speech or appears to lack volume control. Talks too quietly in a noisy place or too loudly in a quiet place.
Speech can sometimes appears to be more advanced than the "average" individual their age. In one case, a boy of 11 years old referred to the weather outside as having "multiple cumulonimbus clouds"
May not relate to other people. Individuals may not know, understand or be able to tell when someone else is sad for instance. Non-autistic individuals may have similar difficulties knowing, understanding or telling when an autistic individual is sad for instance. Can appear to lack empathy. Some theories is that this is due to cognitive inability or lack of theory of mind. A less popular theory is that this is might be due to a different theory of mind. Lack of imagination is often also believed to be connected with this.
Stress or anxiety due to changes in routine. May appear resistant to change. This is not willful, or "bad behaviour" but is part of the condition. For some individuals stress or anxiety may be due to worrying about what changes might involve. Preparing individuals for changes, for example by discussing what can be expected, may elevate change-related stress or anxiety.
Has a particular or "special" interest in a specific topic or topic area. May know everything about the topic or topic area. A hobby that is considered an obsession in clinical terms. Obsession is seen as a slightly insulting term, special interest is preferred.