Another one I learned that pops up in this tale: get on the plane if the meeting is important.
A bizdev friend of mine taught me another: reschedule a call to a Saturday (make up a reason). If it's a serious deal... like, "you're going to be Powerpoint in our office suite"... they'll bitch, but do it.
Sometimes these things are about followup, but a lot of times they're really about qualification; they may just not be into you. It can be important to know that if you're otherwise going to spin your wheels.