When you are meeting someone in a work related environment you should dress smartly and look neat and tidy. This may not be an interview, but you should treat it as if it was. When you are talking to somebody you have not met before it is important that you put them at ease. Do not directly ask them for a job as this will put them under pressure and they may just try and get rid of you as quickly as possible. It is far better to say that you are looking for some help and advice with your job searching campaign - if they happen to mention that they have a current vacancy whilst you are talking to them all well and good.
Most people are generally willing to help other people they know.
Just cross them off your list and move on to the next name. If you know the person well you can just start talking to them as you normally would, e.g. asking them how their family is, etc. Talking to someone for the first time can be more difficult, so make sure you have already thought of a few work-related topics of conversation. You should always show interest in the person you are talking to - do not appear to be totally self obsessed. You should write everything down whilst they are reeling off the names, rather than relying on your memory.