I've skipped ahead a few times when I had an endpoint I wanted to work toward but couldn't quite see how to get there. Sometimes it helps to write out that pivotal chapter first.

For me writing is kind of like reading. I keep writing because I want to see what happens next. :D I know what my major plot elements are but how I implement them is a surprise until I've actually written it usually.

I remember writing the Lyrium War was pretty fun that way. I started that story just wanting a love story with Anders and Neria and knowing there would be conflict with the Chantry. I totally didn't know I was going to *SPOILER SPOILER SPOILER* make that big-badda-boom or... a bunch of stuff.