I found a pretty good article recently regarding subplots. I thought I might as well post it here so you guys could check it out. Also I'm not going to lie, some of the story concept posts I've been seeing recently are quite flat and a subplot or two could certainly help spice things up. Here is the link to the article: http://www.writersdigest.com/online-editor/7-ways-to-add-great-subplots-to-your-novel

I realize that the article is technically for novels, but it can be just as easily applied to games.