I have lots of questions for experts in various fields. Some of the questions are very detailed and based on extensive research, while other questions are more along the lines of "I could research this subject for a long time and eventually find the answer to my question buried in some obscure article, or I could just ask you." The problem is, how do I go about asking these questions in such a way that I'll actually get answers?

I could of course just send out questions to a bunch of experts and see if any respond. But as I said I have a lot of questions, and I'm probably going to have more in the future. (And no they're not the type that I can get answers by posting on Quora or even specialty forums.) So part of what I'm looking for is how do I form a relationship with an expert I've never met? I can't fly all over the world to actually meet them, many of them don't use Skype, and I've never had any success forming a positive relationship over the phone or email.