Everyone has a different style of working, but it can sometimes take time to find it. I would suggest trying different tactics - for example I find it much easier to work under stress so leaving some assignments to the last minute is quite useful to me, also I can't concentrate when working at home with my mother and sister around (even when I can't hear them and they don't disturb me). However, I find it easy to work in my college cafeteria with all the people and noise surrounding me. Just try a variation of study techniques and eventually you'll find the one that suits you. I attended a seminar recently, a man from an education organisation advised everyone that loose paper with notes is the best way of studying, therefore if you come back to a subject you can slot the paper in the right order so everything is together and easier to revise. He also advised that when completing pieces of work the most useful resource would be highlighters and colour. Bringing out the important and relevant information from the page allows you to block anything on the page that isn't relevant and could distract you from the purpose of the work.
So try different techniques, taking notes, using colour, also different locations and noise levels may vary your concentration. Diet can help to, try to eat foods that stimulate your brain (avoiding fat filled foods and treats like sweets and chocolate as often).
This was my first answer, so I hope it was helpful.
