A few tips on minimizing distractions and keeping your concentration during the act of writing.
If you are very easily distracted, you should think about if writing is really what you want to be doing because you're going to find it uphill going. The good news is that all distractions can be reduced, but first it is useful to know the reasons which cause them.
Thinking that the distraction is going to be more fun or satisfying than writing. This is a fallacy. Your writing process may not be gliding along exactly as you wish, but you cannot let the thought of it being a chore to EVER enter your thoughts if have set it on yourself to write. (You can only afford this to happen when you are nearing the completion of a big writing job, and even then you've got to be really careful not to let the quality slip.) Nothing you can do at this assigned moment can be more fun, more interesting, or can make you more content than achieving some true, original expressions of your intellect.
Thinking the distraction is essential to your writing. The voice that says, "I can't possibly begin until I know about this." And before you know it there goes another hour. So you found out more about something - did you need that to start right now? This is a dangerous distraction, especially if you are writing on a computer connected to the internet. If it's getting out of hand, you may have to consider a change of venue. Think then, is reading what someone else has written getting my writing done? Chances are, it isn't.
Unforeseen circumstances. The phone rings, there's someone at the door, the message arrives, you're being shouted, you need to sneeze. Generally, you have to stop what you're doing and see to what it is. Philip K. Dick had his Cosmic Coincidence Control Centre, I've got my Cosmic Distraction Control, where the elves who balance the universe send out distractions in a particle (or wave) form which... well, this isn't the place to get too far into it. The idea is to have a good attitude about these kinds of distractions, to be kind to them.
The next distraction is more subtle than the others because it can occur during the act of writing, and thanks to modern technology, be sustained throughout an entire writing session. It is the distraction that must not be named, and none may dare see its face, for if it were to be beheld at its fullest a million writers would die of the shame of it being known. What am I on about? Music. I was listening to it myself until I wrote this sentence, but it's off now because I feel I must stop listening to music to be able to say something about it without feeling like a fake. Many people work while listening to music, or speech recordings, motion pictures, etc. Many writers work to music, and most everybody who does would say that doing so has no detrimental effect on their work. Taking on original creative work while listening to a recording is different from a task where there is no possible way for the music to affect how the work turns out. The music or words you listen to will affect the way you write, perhaps tonally, stylistically, and it matters. Ask yourself, "Is the music I'm listening to complementing my process, or working against it?" The right music should carry you along so that you are writing at a regular pace - which may mirror the tempo of the music or scene. Or the music invokes your feelings. So it is a collaborative tool, and if you find that you're writing so intently that you're not even hearing the music, then it has to be doing its job. Otherwise, change it or hit the silence. You may find that loved piece of music that got you through an assignment you have been unable to listen to ever since. I've written hundreds of pieces to compositions I've never been able to listen to again. Que sera sera.
The last one comes in pangs or waves, and is bound to strike at least once during a writing week. I'm speaking of loneliness, the ‘Eleanor Rigbys.' As everything you've ever read about writing has told you, writing is a lonely business. It doesn't happen when you're talking on the phone, or typing an email, or in anyway making contact with another human being (unless you're writing for performance.) It's just you and your muse, and if that's not doing its thing you may be leaving yourself vulnerable to ‘getting the Rigbys.' If this is happening, try thinking "hang on, nothing that person says is going to be as interesting than what I'm going to write." Then remove them from your mind, quietly and rapidly, as if by a very professional, very efficient security team.
One effective way to mimimize any of these distractions from occurring is to allow the writing task to distract you from the distraction! Let it become appealing again to you, let your mind wander back, and rediscover your fascination with it. If it really was working before you got distracted, it will exert its own gravity, and you'll be right back into it before you know it.
Now having said all that - I'm off to catch a movie.