I have a shallow box next to my apartment door that I put all my tasks/things to do. Whenever a new thing comes up that I need to get done, I take out a small notebook and write it down, then put it in the box when I get home. Then, whenever I have a lull in the day or am feeling generally productive, I go to the box and start working through things one by one. It's been magic for my productivity and has really helped me keep an organized mind.