Ask people about themselves, their role and their company. It helps if you do some research about who you might bump into, and have an opinion. Listen a lot, be interested. What are they excited about, what's the market like, where do they see the major changes in the next 5 years?But remember it's not an interview, don't just attack them with questions. Talk to them like you would an interesting man or woman at a party, just don't kiss them!