I've heard the "occasionally is nothing, repeatedly is stalking" argument on here repeatedly and (ianal but I know some) this is inaccurate. There are two requirements for a charge of stalking: willfully and repeatedly, and criminal intent.[0] In other words, I can follow you all i want as long as I'm not trying to be stealthy, or I can be as stealthy as I want as long as I don't follow you repeatedly.

[0] http://koehlerlaw.net/assault-theft/stalking/