Whether you're waiting in line, taking a walk or minding your own business in a coffee shop, people around you have a habit of being "friendly" and starting a conversation with you. Only they don't know that in doing so, they are making you very uncomfortable — which isn't a very friendly thing to do. If you're trying to balance your desire to avoid social interactions with your fear that a stranger might think you rude, you've found yourself in quite a pickle. Here are a few tips to get those around you to stop talking to you, without looking like a total dick.
In America, very few people speak another language, so you can safely get out of an unwanted conversation by speaking another language. This gives you the added benefit of avoiding other conversations with people around you as Americans tend to also be afraid of/hate foreigners. If you don't know another language, relax! Just spout gibberish. Another generalization of Americans is that they are terrified of seeming racist, so they'll probably assume your gibberish is a legitimate language and leave you alone.
Apologize and tell them that you're in a rush to a very important meeting. You generally don't have to specify what type of meeting it is, so long as you are sure to leave immediately after providing this excuse. The downside to this is that you do have to leave the area as soon as you can, which means leaving unfinished lattes, purses, phones and anything that'll hold you down, behind. But it's a worthy sacrifice to avoid small talk.
Excusing yourself to the bathroom can give you temporary relief, but it can also be used to get out of a conversation altogether. If you truly want to lose the stranger intent on talking to you about the weather, stay in the bathroom for as long as possible. Generally two to three hours will suffice. Though you may be tempted to, do NOT make fart or barf sounds while in there. It does make the amount of time you're spending in the bathroom seem more legitimate but it could raise concern and force you to interact with MORE people like the paramedics. Just be quiet enough so that eventually they forget about you and leave on their own accord.
This may seem a bit facetious, but if you can convincingly make it sound like your phone is ringing, go for it! Get creative! Try a pop song from 1998 like Closing Time or The Lord of the Rings theme. You'll have to practice this at home. Once you've gotten your impression of a ring tone down, you'll be able to excuse yourself from that annoying stranger without having to leave the area.
Apparently, people are disgusted by germs, so if you act like you have a lot of them, strangers generally leave you alone. First, test the waters by sneezing without covering your mouth. This will scare away most strangers, but if you're dealing with a particularly brave person, try picking at your teeth, ears or nose. This may earn you some stares from the people around you but it'll be worth it when you're left alone.
Sometimes you try your best and still fail. People seem intent on picking at your social anxieties and talking about nothing. So the safest bet is to stay at home where you won't have to encounter anyone else. You might get lonely, but that's what the internet is for. And if you get hungry, order in! There is literally no reason to go outside. Sure you'll probably develop a Vitamin D deficiency and even more acute social anxiety, but you'll never have to fake smile at someone you don't know again.