Mine does not look like a cigarette. When I go out, I stand it on the table in front of me. It is very noticeable. When the server comes over, I point to it and ask if they are allowed to be used in the establishment. Most of the time, I never get to the place where I have to ask. I usually get this: Is that an Ecigarette? Then right after I say yes, the next question is: Does it really work? To which my response is, almost a year cig free! The conversation then goes into them saying: I really need to get one, I've been trying to quit smoking.
After the dialog has started, I then inquire if its ok to use it in here. I don't think I've ever gotten a no. There are some places that I won't even try. Ruth's Chris to name one. High end restaurants just aren't really going to like it. But you never know *shoulder shrug*
I just use common sense as to where I will try and ask.