When it comes to long distance stuff, it's important to make a strong first impression, grab a girl's contact info, trade an email or two exchanging goodwill and telling her it was great to meet her and that I hope to see her again the next time I'm in town or that she should drop me a line if she makes it to my area, and then... disappear. Entirely.

The problem with maintaining close contact or even sporadic flirting long distance tells a woman that you want her as a girlfriend. But she knows that

1) you're not boyfriend material (you don't live there, somewhat of a prerequisite for filling the role of the man in her life that she spends a lot of time with and sees regularly)

2) you also don't have many options at home (otherwise, why would you bother writing her?), which drops your value to her in any capacity.

So, make sure you don't do the sporadic flirting and especially not the continual contact / BBM buddy / Skype friend thing. Women respond far, far better when you resurface after a long absence than they do when you've been a continual platonic (e.g., guy who isn't sleeping with them) presence in their lives.

Keep contact cut until you're in her neighborhood again, and you'll keep your chances at their maximum.