I'd try adding some bits as to what's in it for them. Free marketing advice is really not a good offer. Anyone can get it from the millions of marketing "gurus" that infest twitter. Plus add some details about you and a link to your blog (which is pretty good in itself). One last point is that you want people to know you are not some crazy dude from the internet. Have them see you are just a young entrepreneur who wants to make it. Tell a story, but in less than 4 paragraphs. (:

Shoot me an email if you'd like to some help. I'm a copy wizard. =P