Read The Joy of Living: Unlocking the Secret and Science of Happiness by Yongey Mingyur Rinpoche. It will answer all your questions about meditation, how and why it works, what method is the best for you, etc. You can buy it here.
If you have too many thoughts in your head or even obsessive thoughts, observe them without any evaluations. They can amazingly help you with your meditation. And in some time you will realise that your thoughts come and go and they are not as huge as you thought.
You can use this method on the go if you don't have time for a formal meditation.
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