How to not be scary:

[flamingsword]

One of the most important lessons I have learned is that 'just being myself' sets people on edge. Left to my own devices, I stare, make eye contact too long, and use body postures that have more to do with what's going on in my head than what I am trying to communicate. Just being yourself sounds simple, and if your actions were occurring in a context vacuum where they were not open for misinterpretation that might even work. And with other people who have no social context, it does: Aspies feel comfortable with other Aspies. The muggles are not so enlightened.

So, things that I've learned are creepifying:

making direct eye contact for longer than two seconds.

Watching the person doing something interesting instead of just watching their hands.

Using the muscles of the nose to snarl when expressing disgust, or for almost any reason. To most people that implies violence.

Standing bodily between someone and the only exit from a room. Its a dominance/control behavior that implies that you get to decide whether to let them leave and people who feel trapped are not comfortable people.

Speaking at a volume to be heard over noise without softening your tone is pretty much the definition of yelling. Only appropriate to be used in very noisy places.

Standing at a direct angle to someone who is angling themselves away from you. Mirroring posture is an advanced trick but it starts in the 'don't be creepy' sector.

Have a default expression. Your face being completely blank makes people truly uncomfortable, probably because they only wear no expression when they're hiding something. Also, there's a Hollywood trick of using expressionlessness to characterize madness. Thanks ever so, Hollywood. :/

The specifics of how to be comforting will be the next post, but tell me if I missed something obvious, yeah?

EDIT TO ADD:

Acknowledge the conversations that you are a part of. Use active listening and make noises of assent and interest where appropriate. Do not remain silent when a response is expected. Do not appear to not be listening only to chime in at the end with something that sets the conversation in a different context; people get really upset when what they thought was a private conversation turns out not to have been.

Fierce debate out of proportion to the person you talking with comes across as interrogation and intimidation. Respond to debate with the same level of emphasis as your opponent.

Stand in your own space and not too close to others whose personal space you have not been invited into.

Talking out of turn and interrupting consistently annoys people, and while it's not creepy, it quickly becomes a respect issue and is still socially inept.