How do I avoid conversation with strangers while traveling?

Avoiding conversation is easy: you can get all worked-up in advance, put on a mean face, and look like you're not willing to talk to anybody. However that's a lot of effort and might not be something that everyone can or wants to pull off. Hence I'd rather be relaxed whilst aiming to mind my own business. All in all I assume that some small talk might happen and that there's nothing wrong with that. Also random small talk helps you kill time whilst travelling, and might allow you to meet your soulmate/best friend so don't close that window too quickly.

When it comes to getting out of a conversation, I find that a simple yet polite sentence in the form:

Do you mind if I (get back to my) sleep/read/work since I am tired/want to finish/have deadlines/[add random sensible explanation here] ?

works like a charm. It gives the other person the impression that you are asking their permission to disengage, when in reality you are telling them that you'd wish to stop taking and concentrate on something else. No need to give large amount of details on what you want to do and why. Keep it simple to avoid any counter proposal. Do this whilst keeping a smile on your face, and then get back to minding your own business. Most importantly: do not re-engage after disengaging or else you'll give the impression that taking to the stranger is more important than your other task at hand. This is especially true if that stranger is pushy/bored/chatty etc.

Simple, do not make eye contact. And when you feel their stare on the side of your face do not move your face even an inch towards them.

I suffer a bit from a social anxiety disorder, and as a result, I absolutely despise "making small talk" with anyone because it makes me very self conscious and uncomfortable, so I know how you feel.

When traveling alone, I try to make sure I "look busy" to avoid the uncomfortable conversations. Being busy on your phone/tablet/laptop, especially when it looks work-related, is a good dodge.

However, the most effective deterrent that I found is to seem complete disinterested in what the conversation starter has to say. A few barely interested grunts will deter most people. Only the really determined will try to keep going, and they will usually give up pretty quickly.

I know it seems like you are being a complete jackass, but 99.999999999% of the time, you will never see that person again, so why do you care what they think?

Electronic noise-cancelling headphones will both keep you from interacting with people and will kill some of the noise (especially aircraft noise). You can just turn them on without music, use a tablet, an iPod or a smartphone, or plug into an aircraft entertainment system.

A book or notebook computer also works. Edit: The following is intended as a joke not as travel, legal or engineering advice. (Or you could wear a T-shirt that say "Ask me about XXX" where XXX is life insurance, Jesus, etc.).

In a very few cases you may have to be very direct about it, but I've not run into it so far with legitimate fellow travelers. If you travel outside the developed countries you're going have to get used to telling touts, scam artists etc. to 'get lost' anyway.

If you're attractive it's kind of hard to avoid the opposite sex trying to talk to you, which can get kind of wearying. Try wearing some very dark sunglasses, a hoodie and some massive cans. If they can't see your eyes, see you have on headphones and your head is totally covered they will generally not bother. If they're still persistent, whisper to them in a demonic voice that you want to eat their beating heart before you get beamed back up to the Mother Ship. If they laugh, they're probably worth having a conversation with. If they're freaked and move seats, you win.

I usually just reply to every conversational attempt with "Hello how are you yes yes fine thank you", accompanied by a sincere but very sappy smile. This demonstrates that I do not speak English while giving no clue about what language I do speak. It also gives the strong impression that if you could understand me, you wouldn't want to.

The downside risk is that if I get lost or otherwise need assistance, I have to find a whole new set of strangers to speak to.