Networking and contact information

Hello
I've been lurking these forums for about a year now but this is my first post as I never had much to contribute that couldn't be covered by those far more qualified.

Firstly I have purchased the networking guide (along with several others) which have been pretty informative and helpful. But I am wondering if any of you guys can give me some tips on actually obtaining contact information. I'm a student in Australia, and I'm struggling with my networking at the moment.
I've managed to contact a few alumni from my university, and virtually all of them told me that Australia severely lacks opportunity. In fact, three of the four alumni that responded actually moved to NYC and London to gain employment, and advised this would probably be my best chance.

So I am wondering, what is the best way to obtain contact information with zero connections?
I will be visiting the US this August, so I am going to allocate some time to trip up to NYC for a few days and I was hoping to build a few contacts before that time in order to set up a couple meetings.
I have contacted as many alumni as possible via LinkedIn, but the responses have been few and far between because I imagine people don't check it too often.

Thanks in advance, cheers.