How to deal with a leech student? I've been on a couple of research projects with a few professors and have had some success recently and plan to do more collaborative work through the end of this calendar year.  One student is constantly leeching off of me and imposing himself, such as wanting specifics about my work, specifics about private meetings between me and my research advisors, wanting to come to lab while I am there to do some work. (he is not part of the lab.)  How do I tell this person to back off and do his own work, establish his own connections and stop creeping on me and stalking my every move in hopes of leapfrogging me, just because I've had some recent success?  Do I have to continually say, "this is private and ongoing research that isn't published yet"?
Your time is yours to control. If someone just wants to meet to learn about your field, it's polite etiquette to give them a brief meeting and let them learn... it is a learning environment, after all. It sounds like your situation has progressed well beyond that. I would simply tell the student that due to your own time constraints you cannot continue meeting with him. Consider redirecting him to the department chair/administrators, where he can ask about the process for joining a lab.

For what it's worth, if it's really beyond academic interest and he's just a stalker, that changes things a bit. Definitely work with whatever resources  your university makes available to figure out how to deal with a stalker.