upon first starting out, I practically begged people to tear my story apart and point out whatever glaring flaws they could find. I wanted to perfect my storyline as best as I could before trying to make the doujinshi (drawing's a lot harder to reverse than typing), and I didn't care what harsh comments I got from it. In the end, I just got a bunch of one-line commentaries, and very few in-depth reviews (of them, there was Frostweaver, a friend of mine from other forums named The Big Al, and a couple other random ones). Desperate for more reviews, I tried to advertise my fic more, plug it whenever I could, and begged everyone to nominate it for the fic awards at SPPF. When the awards constantly went bust, I took it out on closet readers (my fic, along with the afforementioned one-line praises, has a very high view count in all the major forums I posted it at.... in fact, if you look at the fic archive, it's second most-viewed only next to "Who Shot Brendan Birch", while falling behind just three others in the current fanfic section. So what other reason is there that I'm lucky just to get one person nominating my fic every time the awards came around?).
It was around this point that I decided to just screw trying to get reviews from random strangers, they probably wouldn't help much anyway. Instead, I took to directly contacting people who looked to be very well-opinionated, people who seemed to know a lot about, not fanfic writing, but manga storylines in general (which is exactly the type of writing I'm aiming for), and as a result, I ended up greatly improving my story upon applying their knowledge, as well as becoming close friends with them.
It's pretty ironic, because when Ida Kathry (Strawberry Delcatty) and Iceking asked me to review their stuff (which I did in hopes that they'd review me.... which they didn't do too good a job at), it didn't end too well... I just said what I liked and didn't like, and then all the sudden, they get clingy, constantly turning to me for all the answers (even though I said I'm no expert on fanfiction myself, especially the narrative stuff). At some point, Ida actually said she was serious about committing suicide over a f***ing fanfic, of all things, and some time after I talked her out of doing that, she suddenly starts blaming me for her problems before convincing an entire forum to hate me (well, as I learned, PE2K's a s***hole anyway XP). At some point, I finally told her off, and though he wasn't as bad as Ida, the sour taste in my mouth over the whole experience caused me to tell off Iceking as well (and he became a total dick afterwards -_-). I don't know why the two scenarios are so different (though I have a few good guesses, as I touch upon in the next paragraph), but in any case, I now see it as a huge mistake to review others just to get word about you spread and/or so they could review you in turn.
I guess what I'm saying is: if you seek criticism in order to improve, you gotta go out there and find a critic you deem worthy, even respect. It also helps that your critic seems very knowledgeable on the subject matter you're after.... it might also help that you not constantly bombard them with questions to a point that it almost seems like you're asking them to write the whole story for you, but rather more subtle questions about the material itself. Ask if they'd advise against this or that, and receive some tips from them, but ultimately making your own decision while still applying what you learned. And lastly, if you get asked to review or give advice yourself, it's advisable that they're someone you're familiar with on the forums (or elsewhere) rather than someone you never even heard of (likewise, your own critic should be someone whom you've talked to before, or who should've at least noticed your previous postings).