I have tried most productivity hacks. In the end what worked best is the Pomodoro 25/5.
I must look pretty special with the amount of notes I take, but it's literally the only way I keep myself honest.
a) Is simple
b) Works for any tasks.
c) Allows for short burst of activity during which it is easy to refrain from reading random stuff, mails, or explore tangential ideas. Easy because you know you will have 5 minutes to check it out if necessary after your burst.
d) Helps for moving around, go fill a glass of water, look at your surroundings etc.
e) Probably correlates well with average human attention span