In most cases, asking yourself "Am I dreaming?" is not enough on its own. Your dreaming mind is almost always firmly convinced of the reality of the dream situation, no matter how unusual or bizarre the situation may be. For this reason, it's necessary not only to ask yourself if you are dreaming but also to take other very simple steps at the same time to determine whether or not you are within a dream.

On top of that you should use autosuggestion (suggest to yourself that you will have a lucid dream either that night or in the near future through the use of mantras and imagination) a few hours before you go to sleep and when you go to sleep.