I'm not sure that writer's block exists, or if it does exist then I think it just never really goes away. I've never really sat down to write and not felt at least a little blocked but I've also never really ever been unable to push through that block. I guess I do a few things to make 'pushing through' a little easier. First, before I ever writer anything I outline a lot. I map out not only a book, but an entire trilogy. I map out plots and character growth chapter by chapter, book by book. I try to leave room for unexpected surprises to occur as I tell a story (and many of my personal favorite moments in my books were unmapped surprises) but I like to outline as much as I can so that when I sit down to write I have options of what I write that day. I also reread and edit whatever I wrote the day before prior to writing anything new. That gets me in the mindset. Finally, when I'm working on a book, I'm thinking about it all the time. In the shower, on a jog, driving, doing yoga... whenever I can tune out a little I think about my characters. There are always in my head. I find that I tend to be chomping at the bit to get writing rather than feeling especially blocked.