Here's a good article about how to write good content. 

One point is especially useful, I think.  That is that the more content you have there, the higher you go in the rankings. 

I've discovered this through blogging.  Certainly, it helps to submit your blog to directories, post comments, etc.  But by far the best approach is to just keep on writing.  The more words you have out there in the ocean of words that is the internet, the greater the chance Google will notice you. 

The other main point:  Speed.  So many people are churning out the content like crazy so you've got to do the same so as not to end up at the bottom of the pile.