David start-up vs industry Goliath

I'm sure many of you here used to work for some larger company before going on your own. I used to work for a 'larger' company myself too before they screwed me over; I was "just a hacker" at the time so none of them took me really seriously.

Now it's payback time: I've been working (and still am, ofc) on a start-up that will compete directly with them. The product itself is light years ahead so I have no doubt it'll get a great percentage of the Goliaths' sales. The questions I can come up with would be:

1. how to use Goliaths' strengths and weaknesses as my own advantages? I've read on this topic lately but still really want to hear fellow hackers' opinions.

2. how to "push" my start-up with practically no funding in a 2nd world country? I'm not looking for funding, going the 37signals way on this one. Except for the idea being super awesome and packaged in the simplest interface possible, I pretty much rely on word of mouth and SEO. Ok, and social media (which I have no experience with). Is there a "pushing your start-up for dummies" book or blog?