First of all, I absolutely agree with what throwaway420 said about not putting Google on a pedestal. I wouldn't advocate making
any company (other than one you start yourself) such a "huge life goal". Yeah, Google have a lot going for them, but I'll bet you there's plenty of negatives about working there as well. And as big as they are now, there's no way there isn't a significant level of bureaucracy and typical corporate B.S. Just read some of michaelochurch's comments[1] here on HN sometime for a different view of Google from the inside.
Anyway, that said, if I specifically wanted to target Google, I'd do this: Find one of the many OSS projects that Google run, and get involved. Start submitting patches, get your patches accepted, and become a valued contributor to the team. Make it a point to follow Google emmployees on G+, Twitter, whatever, and pay attention to what they're sharing and discussing. If you see an interesting topic, bone up on it. Read the various Google blogs. Stay on top of what topics Google are showing an interest in and become knowledgeable on this stuff. Post share stuff on G+, Twitter, etc. that demonstrates your knowledge in these various areas. Network with all the Google employees you can (without doing any creepy stalkerish stuff!) and build credibility with them. At some point, if you do all this right, they'll probably start trying to recruit you!
Bonus option two: Start a startup that gets acquired by Google.
[1]: http://news.ycombinator.com/threads?id=michaelochurch