Improve concentration

1. Find the right place
When I was a student at university I almost failed the first semester, because I could not learn effectively. In the second year, I decided to find a place where I can focus just only on the books I have to learn. This place was the university library, and I passed every course with very nice grades.
Another example, never work in your bed, your brain is associated with your bed to sleeping, not working.

2. Candle exercise
This is one thing you can do at home in the dark.
Take one candle, ignite. Just focus on the light, forget your thoughts, do you see the borders of the flame? If yes then you are focusing finally, ok now let's try to warp the light to left or right, only with your consciousness.
Did anything happen?

3. Take a break and breath
Your body always knows, when he or she lost the focus, he or she starts to wonder or doing things that are off-topic. When this happens, just go to walk, make a cup of tea, open the windows.

Improve productivity

4. Make a to-do list or step planstodolist
Yes it sounds terrible, but you need only a paper and pen. No big deal just write down what you have to do, it will increase your productivity because your mind starts to focus.

5. Do only one thing at a time
Working on several things simultaneously causes, no progress in either.

6. Rank your tasks according to their importance
80% of your tasks are not worth to work on, start always with the important things. If there are too many things in your mind, throw your to-do-list and start a blank one.