The only tried and true method for me is to write. lol. Writer's block is usually a lack of inspiration or insight into your story. Sometimes the best thing to do it to let that story rest for a while and work on something else.
Research, watching movies or TV shows, going to museums, or exercise can all help as well. Often, while doing those things, I'll learn a fact or hit on an idea that will inspire a new scene. And then things are flowing once again.