Most autistic people have some kind of social anxiety. This is a list of some of them:
Do not like making eye contact: This can be for a number of different reasons. One of the main reasons I've heard though, from autistic people, is that they have trouble looking into someone's eyes because they can not predict what that other person is going to do and that's scary. Another thing that I've heard an autistic person tell me is that when he looks into someone's eyes, he feels as though the other person is looking straight into his soul and it makes him feel very uncomfortable. Some autistic people simply look away from the person talking to them because they can only focus on one or two senses at a time and for him to be able to listen to the words being spoken to him, he has to overturn his eyes or close them altogether so he can concentrate on what is being said. It is not a sign of disrespect and is in fact a sign of great respect because the autistic person is doing everything he / she can to communicate.
Do not like being in public places: Autistic people have trouble sometimes going out into public places because they can not control their environment. Out in public places like a department store for instance, the autistic person feels like he or she is having stimuli violently thrown at them. Most people can block out background noises of the checkout stands beeping or muzak playing overhead or of other customers chatting. This may not be so for the autistic person. Instead of being able to focus on what their friend is saying and letting the rest of the noise fall away, he hears EVERYTHING THAT'S GOING ON REALLY, REALLY LOUDLY AND ALL AT THE SAME TIME! It can be quite unnerving to have to go through that. This can sometimes be remedied by wearing headphones but these can not be worn all day long or their sound sensitivities will become even more pronounced.
Do not know what to say in any given situation: Most autistic people, for reasons unknown, do not pick up on the minority nuances of non-verbal communication. This means that they are missing out on about 80% of human interaction because only about 20% of our communication has to do with our language and what it actually means. The rest has to do with body language, facial expressions, tone of voice, inflection and unwritten social rules such giving others their own personal space. For the autistic person, these things have to be taught, almost as if from a text-book, the way you or I might study arithmetic or language arts. Some autistic people do not even pick up on verbal communication at all, and many of those who do have trouble expressing it properly. This can cause a lot of anxiety when he or she is trying willingly to communicate and can cause frustration when they are not able to.
These are a few of the reasons that autistic people have so much trouble in social situations. When dealing with an autistic person, it's best to use patience and understanding. If there is something that he or she is doing that really others you or seems inappropriate for the situation, the thing to do is to tell them exactly what it is they are doing that's weird or wrong and why. Then tell them what is appropriate in that situation instead or when it would be appropriate to continue that behavior. Be kind about the way you correct them because it is highly likely that the autistic person either really did not know how to handle that situation or they forgot. It may seem to do this at first, and in most social circles, it is but when dealing with an autistic person it is best to be open and honest.