Are you awake now or is this a dream? While slightly mind-bending, asking questions like that and performing reality checks can help you take control of your dreams through lucid dreaming.
Lucid dreaming can help you tap into creative powers not available when you're awake -- perhaps for that next scientific breakthrough or ingenious idea. The two-minute video above from AsapSCIENCE explains how lucid dreaming works and several methods you can use to practise lucidity.
Besides keeping a dream journal (perhaps on previously mentioned Lucipedia), one easy method is to perform reality checks often when you're awake so that it becomes second nature. For example, check the time, look away, then check the time again. This increases the odds of you performing the same reality checks when you are dreaming and consequently realise you are asleep.
The Wake Induced Lucid Dreams (WILD) technique, however, is not for the faint of heart, given the potential for sleep paralysis and hallucinations. Once you get started with lucid dreaming though, you can turn nightmares around and have extraordinary experiences while you sleep.
The Science of Lucid Dreaming [YouTube]