The Den of Amateur Writing was founded on an old principal of "give what ye wish to receive" that is somewhat alien in today's internet. With the exception sites like Stack Overflow, most sites model themselves after the social network. They promote the "look at me" moniker of posting content and waiting for people to comment and rave over it.
On The Den, writers take time to comment on the writings of those who comment on theirs. Obviously, this chain requires someone to go first. To get the ball rolling on The Den, you should rate and comment on the writings of others. Doing so will show you're here to be part of the community and encourage people to return the favour.
Rating writings does a few things to help you and the writer. For starters you must start to think about the varying pieces that make up a good writing. Second it makes you start to think about what areas of the piece can be improved.
Often it can be difficult to see these things in our own work until we've had practice. By taking the time to rate writings, we train ourselves into this critical thinking process.
Once you've warmed up the thought process by rating a writing you should be ready to provide some useful feedback that helps the writer improve the work. Be sure to weigh both the good and the bad of the work, and highlight areas that can be improved.
If you have difficulty understanding the work, getting into it or find the flow difficult to follow when reading; think about why. It's important to articulate this to the writer to help them improve these areas.