To improve concentration you need to get your brain involved with the world around it. This will obviously help you to avoid daydreaming. Generally when concentrating it can be more interesting to think of something else, like for example what you are going to be doing at the weekend.
How to get your brain involved with the world around it:
Think about a situation in your life where you need to pay attention, it doesn’t matter what it is. It could be a lesson at school, college or university. It could be a work meeting or whatever you like. Just think of a situation where it is necessary to listen and pay attention.
It's easy to start daydreaming when listening to someone else talk, especially if they are talking about something boring.
Therefore in order to concentrate you need to get your brain involved. To do this you have to be asking yourself questions as you listen.
First start off with general questions:
What is the topic of the lesson or meeting?
What do you already know about the topic?
What are the most important issues?
What is the overall message the speaker is trying to get across?
Then think about the specific issues:
Who is involved and what do you already know about them?
What is going to happen and when?
Where are things or events taking place?
These are only examples obviously you only need to ask yourself questions that are relevant to your situation.
The point is that by asking and answering the questions you are forcing your brain to think about the topic at hand.
When the person is talking and they say something you don’t really understand try to make an educated guess. Ask yourself, based on what you already know, ‘what is it most likely to be?’
One way or the other your brain is always going to be thinking about something. It will simply wander away to the most interesting thing if you don't have control over it. By asking yourself questions you are forcing it to think about the topic at hand. This is the easiest and most effective way to improve concentration.