The one thing I do that benefit my productivity and creativity the most is taking breaks. There were so many times when I was overwhelmed by a diffucult problem, only to find that a quick five to ten minutes break was I all needed. It's needless to say that after such a break I would normaly find a solution to my problem.
It's scientifically proven that one break an hour can boost your productivity. Our brains numb out a bit to the constant stimulation, and we become unable to continuously treat the task as important. Taking a break allow us to regain the energy and sence of purpose.
Document your daily progress. I've been practicing this for a long time and the benefit of this activity is undisputed. Documenting progress gives you a sence of accomplishment. It also provides information about your current productivity state. That way, you can find interesting patterns of how you work and optimize your workflow when you gathered enough data.
Forget about multitasking. It's the number one productivity killer. Focus on one task and try to reduce context switching at any cost. A constant focus switching is known to decrease the effectiveness by two to three times. You need relatively five to ten minutes to regain focus and become "in the zone" again.
Learn how to use your IDE or editor. Becoming a master of your tool will increase your effectiveness. For example, I use Webstorm at work and at home and I've invested a serious time learning how to use it to the greatest degree. That is, but not limited to, shortcuts, integrated features, templates, workflows, etc.
Plan first, code later. Making the right decisions is a vital part of our developer work. Planning the implementation design first is a must for every task and every problem you want to solve, that being a new feature or a small bug fix. In our company we make design documents for every new implementation and discuss it with the whole team. We make sure we cover every edge case and every possible regression. When all of us are at the same page, we can start coding.