Increasingly, I've used begun to listen to music while doing nothing else. I concentrate on the music itself rather than using it as background. When I meditate, and dismiss other thoughts that come up. When I am teaching, I am doing that. Nothing outside the classroom discussion exists for me. When I'm talking to a friend, that person gets my full attention.
When I write, I shut out other distractions. It could be in a crowded, noisy café, but that's what I do.
The secret of concentration is very simple. Don't multitask. Just devote yourself to whatever it is you are doing. It's true that I recite Shakespeare in the shower, so that while I am showering I am not only showering. Most things, though, are worth doing for themselves, without any other activity interceding.
If you think you can only concentrate for 10 minutes, then start there. Work on your project for exactly 10 minutes and gradually work up from there. You really only need to be able to concentrate for 25-30 minutes in order to make good progress on a larger project. You can write for 25 minutes, take a break, then do it again. Once you are used to concentrating it becomes habitual. You can turn your email off for those 25 minutes, because nothing is that urgent that can't wait such a short time.
I can concentrate for three hours on a project. That's about my limit, but I rarely have to work 3 hours a day on my research and writing. It's nice to know I could work three hours straight and think of nothing else, but I almost never have to use that excess capacity because I can accomplish a tremendous amount in 2 1/4 hours.
Often, I will tell myself that I have no concentration on a particular day before I even try to work. A huge mistake. It is much better to work anyway and then have the *concentration habit* quick in once you begin. The worst that can happen is a mediocre writing session that keeps in touch with your project. On days I don't feel like exercising I might go to the gym anyway. I tell myself: "I will go to the gym in my gym clothes even though I am not going to exercise at all. " Then, once I am there, I figure out I might as well work out.