Use a timer, set it for five minutes to start with. Work hard during this time and then move the timer on to ten minutes with a short break in between. If the task is sedentary, get up and move around during the short break. This will insure better concentration. Utilize some sort of relaxation training such as neurotechnology before you undertake a difficult task.
Meditation is useful but is very difficult for some individuals.
Set up all tasks in little sets with the same needs and outcomes. This can be thought of as breaking up large assignments into small tasks. You will gain momentum as you accomplish each little task and soon the larger one will be finished. Work within a clean environment keeping yourself free from distractions that will occupy your time. If you are a professional person working outside the home, try to budget your funds to allow you a housekeeper at least a few hours weekly.