Summarize:

Autistic people deal with barriers and stressors that neurotypicals never face, so they may act unusually or exhibit different social skills. This depends on the individual's needs and strengths.   People with stronger social skills may simply seem awkward and a little clumsy. They may have difficulty understanding what is expected of them, so they may say or do things that are surprising to you. Some autistic people face large conversational challenges, and may not be able to carry a typical conversation. Eye contact can feel incredibly overwhelming, and the autistic person may not be able to meet someone's eyes and listen to their words at the same time. Explain that for autistic people, looking away is different from not listening.   Never force eye contact. This could make them scared or uncomfortable, their conversational skills may plummet, and it could trigger sensory overload. Some autistic people are capable of making or faking eye contact without it bothering them too much. It depends on the person and their comfort zones. Teach the person that autistic people may need to fidget or avoid eye contact in order to focus. The autistic person might look at their conversation partner's mouth, hands, or feet—or even in the opposite direction. Becoming angry with the autistic person will only make the autistic person avoid them.   Due to sensory and attention differences, it can be hard for some autistic people to focus on a conversation. The autistic person is not ignoring other people; they may be struggling to take part in the interaction at all. Teach others to make it clear when they want to talk to the autistic person. The person should be physically close, use the autistic person's name, and preferably be in the autistic person's line of sight. If the autistic person doesn't react when addressed, try again, because they may not have noticed. They have a hard time understanding different tones of voice, particularly when the facial features of the person talking do not match the tone of voice.   When explaining this difficulty, you could liken it to the use of emoticons in texts. If a person were to text you “Well that’s just great”, you may assume that the person is being sincere. However, if the person uses an emoticon like “:-P” along with the text, which stands for someone sticking their tongue out, you would interpret the text as being sarcastic. Autistic people can learn to understand figurative language. Some are quite well-versed in the nuances of sarcasm and humor.
Explain that autistic people may act a little differently, and this is okay. Mention that the autistic person may not make eye contact. Explain that autistic people are different, not necessarily disinterested. Note that the autistic person may not understand sarcasm, humor, or tone.