Having tried everything, nothing works better than 5x8 yellow pads. Write down everything you need to do. Draw a line thru when done. Every few days, rebuild the list. Everything has to be on one page, or there are too many to-do's, and you can delete ones that just don't make the cut. No technology, just pen and paper.
Now I have a company and a team so we use an issue tracker, which I find to be much much heavier but it's easier to use across multiple people.