Following up on preliminary phone calls?

What is the best way to follow up with somebody after speaking to them on the phone? I recently spoke to an MD over the phone and requested a connection with him on LinkedIn. I'm not really sure if it's normal to email him a few weeks after speaking and ask him questions about the markets, investment banking, etc.

What kind of questions do you normally ask to stay in touch with new contacts before you need some sort of help finding a job?

Thanks for any help.