When this little Nook first came into being, I don't think the discussion groups even existed. However, some basic rules that have already been mentioned about comments apply equally well to the groups and so I'd like to discuss them here.
When you use the group discussion boards, don't post the same thing multiple times in multiple forums. This is considered spamming and is highly frowned upon. The posts will only be deleted and you'll be warned you should not to do it again else more serious measures need to be taken.
Spamming the groups is more annoying for readers than anything else, and no-one likes spammers so instead of attracting people to read your story you are in fact more likely to make people not only avoid it, but avoid all of your work in future because they know you are a spammer. Certainly I feel this way and I know I am not alone in this attitude.
If you want people to look at and collaborate on your story the best way to achieve this is with a single post in the Collaborative group forum and contacting people you have worked with before who you think might be interested directly. I stress that you should approach people you have worked with before, or perhaps know from elsewhere. Unsolicited, direct messages are just as bad as other kinds of spam and will earn you as much bad will.
If you comment on other peoples work and those people seem like they may also be interested you might suggest taking a look at your story in your comments as well. The key thing is not to be too pushy as people often dislike advertisements, pushy ones doubly so.
As in virtually all cases, think before you act. Would you like it if you were swamped constantly with requests to view other peoples work? If you saw the same advertisement everywhere you went, over and over again? A lot of people hate that kind of thing and they'll hate you for inflicting it upon them. Nobody wants that.
I know it can be frustrating if nobody comments on your stories, but remember, a lot of people are in exactly the same position. Rather than make other people frustrated for other reasons, try removing that frustration entirely by commenting on other peoples work. Try using the "Surprise me!" random story button or browsing the stories page and commenting on a lonely piece of work and you might be pleasantly surprised at the responses and make some new friends too.