Treat these meetings as a learning experience. Dress smart, present yourself like you would if you were on an online interview.
Ask questions, do not dominate the conversation. Show interest in the other person, remember you are here as much to learn and then share!
A cardinal mistake people make is ask for something the moment they meet someone. That is a no-no in networking. First offer something of value to the other person, and then ask for help that is equal to what you offer.
Some topics you could use: