This is the first website that I went on when I decided that I wanted to be an author. And it taught me a hell of a lot. Though, my YA story did suffer a death because of it, but out of its stomped on ashes "Behind the Hood" was created.
What I learned the most from youwriteon was the techniques of writing a story and getting the attention of the reader right from page one. A few of the techniques that I learned was to not start off with so many gerunds at the beginning of a sentence (-ing words), to be careful about repeating a word too close together, and to show and not tell... This last one, to show and not tell, is still damn hard to do even after writing for a while, and is why an editor is important because they see what you can't or have missed. If you can't afford an editor then you can find someone in the same boat as you, from this website or one of the others, and do an exchange. But the show and not tell gig is more important when one is writing for adults, because they don't need the same information that the younger reader does.
However, if you do go on this site don't take everyone's word as gospel. If you don't agree with someone's assessment of your work don't do anything unless you get more people repeating the same thing. Also, some people say that getting reviews are slow in coming. I didn't have this problem, but I have been told this.
If you want to join youwriteon, they take the first 7,000 words of your story, so it's a great tool to set up your book. But, if you want advice on more of your story then Authonomy is a place that can help you with this.
Authonomy, authonomy, authonomy ... a lot of fun, but can take over your life if you want to go for that editor's desk ... which may not always be worth the effort. Plus, you will get loads of people giving you a one line review telling you that your story is brilliant. I cottoned onto the bullshit pretty quick, because those reviews are just a waste of your time and are only written to get your backing. Also, you will get people spamming you in the message system, trying to talk you into backing them. This backing system is totally different from youwriteon, where you can get some very harsh reviews.
HOWEVER, all this said Authonomy is still very useful and has helped me greatly. Even though you get a lot of self-serving people on there, there are also those gems, the people that will go out of their way to help you, or just give you honest reviews and good advice. So, the best thing to do with Authonomy is to not get a bloated head with all the "love" given out, and to find the right people to do reading swaps with.
The forums on both Youwriteon and Authonomy can also be helpful, as well as a little bit crazy. You guys from Authonomy know what I'm talking about :)
Both sites also have an editor's desk, but don't go in it for that as it's unlikely that you will get your work picked up through this avenue. The most important thing is to go on there to better your work.