Best bet would be honesty. "You caught my attention..." Then go into a topic.
There's a book out on the web called "Window Shopping For Women". It's all about internet dating specifically on websites like MySpace and Facebook. It's got a lot of good advice in there on setting up your profile, getting social proof online, and how to initiate conversation.
You will probably want to come up with your own scripts for it as when I tried it I got called out a few times (which is not a big deal in the least), but for better returns on your time spent write your own. I had one girl ready to meet me within 5 messages using it.
The only con I really found to it is, it is still very much a numbers game and if you live in a pretty small town you might have some difficulties.
Best of luck.
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Sincerely,
Jack Sunday

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