Look upon everyone that you meet as a possible friend. Don't ever assume that people aren't going to like you, for whatever reason you've already pre-determined. They don't know you - you don't know them - you're on equal ground and they're probably as nervous as you are about instigating a conversation.
Small talk can be about anything from the weather to a program you saw on TV yesterday - if you think it's relevant to the situation you're in.
Use open ended questions in order to encourage conversation. For example - if you ask someone if they had a good journey their possible answers could be Yes or No. If you ask how their journey was or how they traveled here - this expects a lengthier response from which you can develop into a discussion.
When the conversation is flowing you have the opportunity of finding something in common with which to elaborate.
Respect Other People's Views
If someone presents a totally different viewpoint from yours, it's essential not to try to put them down in any way or show off your knowledge, (especially if there are others present). This makes it look as though you're putting someone down and even if you're right, onlookers will feel uncomfortable.
On the other hand you shouldn't feel that you have to agree with someone if you don't really believe they're right. You can respect each other's opinion and agree to differ, quite amicably.
Recognise People's Personal Space
Many people in Western societies avoid close proximity with others, unless they are 'connected' in some way. Invading that personal space is like invading someone's privacy. The ideal length of that space is approximately 18 inches, although you will notice strangers standing closer together if they've no choice, for example in a crowded train - however they're unlikely to feel comfortable with this.