A useful technique to start writing is to sit and begin writing the key scenes of the argument. If the plot is well established and you know your characters, the scenes, and the development of the story, then you will be able to define which and how many key scenes there will be. And, you will definitely be able to define the important, intense, and emotional scenes that you’ve dreamt of while forming the story in your head.
Starting to write from one of these “hot spots” will motivate you to produce page after page without feeling blocked in front of a blank sheet. Non-consecutive writing tends to fix the key points of the story just as we have imagined. It also permits the filling of intermediate spaces, this way your novel will be heading for the right direction from the very beginning.