I generally use the Pomodoro technique (25 mins of focussed effort, 5 min break, repeat). One thing I find useful to stay focussed, is when a distracting idea

I generally use the Pomodoro technique (25 mins of focussed effort, 5 min break, repeat). One thing I find useful to stay focussed, is when a distracting idea comes to mind is to simply write it down somewhere, so I can look into it later. If other people are a distraction, you need to make some time where you cant be interrupted. Switch your phone to airplane mode. Tell people you are working and not to disturb you at certain times, or just let them know you will get back to them later. If you aren't a jerk about communicating this, most people are pretty reasonable.