One thing I've discovered over the years is that asking someone to do the tiniest bit of real work is an unreasonably effective way of separating out the posers from the operators.

Say something like "I'd love to meet with you but I don't want to waste your time so I'd like you to send me X first so I can look it over and come up with N suggestions before we meet". Make sure X is something that needs to be generated rather than something they might already have on hand.

I've found, when doing this, that all the marginal requests magically melt away and they will simply stop responding to your email and never contact you again. It doesn't matter how trivial the request is, I still can't quite figure out why it's so effective.