I see the people around me as a valuable resource. Everyone has something of interest and everyone has something to give but more than that you have means of helping them which can cost you nothing.
Think back on the major points of progress you've had in your life, for me, many of them are due to the people I've known and met. Jobs came through word of mouth rather than search and apply. A lot of the best, unexpected yet useful knowledge gained has been through direct contact with people.
Standing in line saying nothing I feel there is this great resource, under utilised.
Someone who can utilise this and find a way to break the social barriers will increase chances for serendipity. It seems like there is a network between people that is operating whether you interact or not. The people who actually interact ake greater advantage of this. The network is interesting with this effect in different ways if you're staying in the same place or traveling.
So how do we do break the ice?
Well if you're British you mention the weather or get drunk, but is it going to go any further than that? Likewise, how do you get the subject onto something more interesting, avoid the awkward silences and so on?
I'm no expert in this but I know the only way to learn is by doing taking any mistakes on the way as valuable lessons.
What are your ways of breaking the ice?