You have to find out what works for you — sometimes down to the very fine detail. Should you stay up at night and draw into the late hours? Should you get to bed early and rise with the dawn? Do you need coffee to get started or a very cold bottle of water? What kinds of notebooks are appealing? Have you ever wondered what it would be like to spend a day going round with a small notebook drawing random sights?
Or perhaps you do that all the time, and what you need is to choose some very complex image and work at it relentlessly. Do you work from life? Make drawings from memory? Have you investigated things that artists did in history and apply them to contemporary motifs? Do plans and schedules keep you on track? Or are you the sort of person who needs to feel spontaneous?
Whenever something isn’t working for me, I try something else. Sometimes I just start drawing in medias res because I’ve lost the thread of my ideas. Then I find that just moving my hands jump starts some thought process, like a dream remembered, and I rediscover the thing hidden in my mind.