Americans are generally quite willing to strike up a conversation with complete strangers at the bus stop, on a plane or in an elevator. They are in a common situation and if there is something neutral to comment on (how slow the buses are running, the weather, the scenery), it is perfectly normal for either party to comment to the other person.
A common gambit is “It sure is a nice (awful) day, isn’t it?” If the other person simply says, “Yes, it is,” then you should take the hint that he or she is not really interested in extending the exchange. But if he or she says, “Yes, and I heard on the radio that it’s going to stay like this,” that person has indicated a willingness to participate in conversation. You can break the ice yourself, but if the other person is not interested, then do not pursue the matter.
To keep the conversation rolling, avoid asking questions that anticipate a yes–no answer or a one–word answer. Questions like, “What is your favorite color?” bring a conversation to a complete stop. Learning the answer to such a question really does not help you learn about the other person and does not lead to other topics. Questions like, “How long have you lived here?” allow the other person a chance to introduce his or her past. That will provide a basis for further conversation.
If two people are at a conference or a reception following a speech, they automatically share something in common, so that would become a subject of conversation. Imagine that at a large party following a lecture by a well–know speaker you are standing next to a person at the buffet table. You might start out with, “That was really a stimulating speech, didn’t you think?” or “This roast beef is really delicious. Have you tried some?” If the person responds, you may want to introduce yourself: “I don’t believe we’ve met. My name’s Hiroshi Ohmura. I work for the ABC Corporation.” The other person would respond, “It’s a pleasure to meet you, Mr. Ohmura. I’m Alex Smith. I’m with the Chicago Tourist Bureau. What kind of work do you do?” With the last question, Alex keeps the conversation ball rolling.