It has to be practised, first you have to remember your dreams and maybe write down reoccurring features in you dream... for example things that happen a lot, this is the case for everyone. After that you need to make sure when you are in the awake state you realise the signs of being awake. After you have done that... next time you sleep you will realise that you are dreaming and not awake... For example, if you have enough will power if you are dreaming a house and the light starts coming on by itself you can realise it is a dream and then you can start "controlling it" so if you want to fly, you can start flying. You have to see the signs of being awake and dreaming first before you can lucid dream, inshAllah.