Lucid dreaming is when you’re dreaming and you are aware that you’re dreaming. There are various levels of lucidity. When you know you’re dreaming, you’re more likely to have the ability to control that dream. You can do what you want, since it has no consequences. There are certain signs that can tip you off as to whether you’re having a dream or not. Here’s my current list:

• Deja vu – I have never experienced deja vu when I’m awake. I think it comes from previous dream experiences which are only remembered vaguely.
• Wondering whether this is a dream or not – If I have to ask yourself if I’m dreaming, then I am dreaming. When things are real, I have no problem identifying that they are real.
• Flying – This isn’t just restricted to flying, actually. It also applies to when gravity is not working properly.
• Eyes not opening properly – Sometimes I have problems with my eyelids when I’m dreaming.
• Changing scenery/Unstable environment – This is a sign I have in my head, but it’s almost never the one that manages to tip me off.
• Being lost in a place I know well – This isn’t quite the same as the previous item. This environment is relatively stable while I dream, but the place is way off from what it should be while awake. Sometimes, this manages to produce deja vu.

There are more, but I’ve yet to actually use them.