This is coming from me (I'm diagnosed high functioning autistic--believe me there has been a lot of stares)
So here is my advice and my short story of what happened a few times:
This boy had been staring at me a ton, and I was sure it was because I was acting different....at first I was going to be mad, but then just handed him an awareness card from
http://autismcards.com/ , and he looked at me and said "I know what this is..." I said,' Yeah? ' What do you know? And then he said, I have Aspergers Syndrome... He said something really unique though, so I thought I'd share! It was pretty cool and cute

He said,' How would you know I'm staring at you, you must have been staring at me then to see I was staring at you?' Cute, ha?! Actually, kind of true... Now I'm thinking I am going to start being really careful, or really I usually don't get mad but see it as an opportunity, so really for the others who stick up for me, since you never know the person might have a disability too...
Also, I'm thinking its better to just have those along than get mad because then the other people the next time they see someone w/ autism will have a bad repor

, so I've found personally those work the best... Check them out, not a lot of shipping charges either and get a lot for one thing.
Also,
Gotta add this!
I stare sometimes a little because I see a person and I wonder if they know their child is Autistic... I had a lady and her son was throwing a tantrum in the bathroom where I was... I was kind of staring...psychologists do a lot too I think, lol since its their job I guess... and she got really mad and started cussing at me and saying why are you staring? You are soooo rude... I didn't say anything I just pulled out a couple of fidgets, turned on the water put it in my hands, leaned down and he stopped tantruming... I pulled out a small card... and then she was staring at me, and she said how did you do that, and I said, "well, it works for me and other people with autism..." Then she started getting teary and ended up saying "Oh, my God", I've had that in the back of my mind, but I was really trying to think he didn't have Autism, and then started thanking me a ton and saying she was going to go get him observed and tested for Autism... ended up, he was Autistic... so I gave her the same advice for if others stare at her son, they might be a psychologist, another parent with a child of an Autism Spectrum Disorder, high functioning Autistic like me, or just a person who just is curious or doesn't know what is going on... sometimes people stare too, its sad though, because they want to make sure the child is safe...if you know what I mean, its sad, but at least its a reason... That's where those awareness cards really come in handy... and its actually helped some people that they have turned around and asked if they could help a mother who was in the middle of something when their child was having a meltdown... it really pays off!!
I forgot to add, also there are buttons your child can wear and t-shirts, the site also is
http://buttonsandmore.com/ and it is pretty cool buttons too. And, of course, autismcards.com has great cards... Buttons are good too though!
Kris