Have some general topic on hand: Weather, news, politics, sports, etc.
Also some of your own interests, his/her interests.
Pick up from there, ask questions on the others' point of view, give your point of view and open answers/questions (gives spaces to ask questions/gives answers on for other people).
Here is a link on open and closed questions:
http://changingminds.org/techniques/que ... stions.htm
There are two or more in a dialog, so to keep the conversation running all have to do some effort or atleast two.
Taking initiative helps the conversation along but give space for others to do so to in the silences in-between and between topics for others to file in.
All I can think off at the moment, but I am not the only one in this discussion . So, I'll give space for other people to answer some more or comment on mine.
Cheerfully,
Wallourdes
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"It all start with Hoborg, a being who had to create, because... he had to. He make the world full of beauty and wonder. This world, the Neverhood, a world where he could live forever and ever more!"