That's something that I struggled with recently and I finally decided that my ego was getting in the way. I hit a point in my story, which was great at that point, but I hit a dead end. I didn't see where the story could expand from that point, so I started on ideas for the next book. While in the midst of developing new ideas, it came to me that I had stifled my characters and I needed to go back and write an alternative version starting a few chapters before my brick wall. Let me tell you, it was hard and I'm still not recovered, but the characters are now leading the story instead of me.
I guess the best method for me is to step away from the project for a time then come back and read it to see if new ideas strike me. While it was hard to put it away for a time, it has been fruitful.
I hope you're able to find a method that works for you and that your ideas may flow like Niagra Falls. By the way, if you find something that works for you definitely let me know. I'm always open for pointers. Best of luck!