Pick the most important thing you need to do now and attend to it totally at the exclusion of all else until you finish it.
Sounds simple, however, it is amazing how easy it is to side track.
The side tracking can happen through your phone beeping (phone ringing, a text or what's app message or VIP email coming in) or through someone interrupting you or another thought cropping up in your mind throwing you off tangent.
The key is to stay the course on what you are doing and not allowing any of the interruptions any opportunity to distract you. Ideally, you want to put your phone on meeting mode so there is no beeping and working in a place where no one can interrupt you.
Why is this important? Interruptions can be the biggest time waster and also a big drain on productivity. One minute of interruption is twenty minutes gone!