I didn't see anyone else mention it (sorry to repeat if someone does before or while I write this).

But it REALLY helps if you have a friend who is already in there refer you. If you have none atm, either network or use http://steve-yegge.blogspot.com/2008/03/get-that-job-at-goog...

Having a referral pretty much lets you skip the majority of the line at most companies. It also lets you get by even if your resume is not particularly stellar but your skills are. Google, in particular, makes an effort to do onsite interviews with most referrals (unless you disqualify yourself via a variety of different ways).

Having a friend there also means you get a lot of help along the way, advice about what to study for, hints, etc. So all around, its a good idea.