[OnMyPhone]

I'm not who you're replaying to, but...

When I was learning how to lucid dream, one of the triggers that I used to tell I was in a dream was flipping a light switch on and off. When I saw nothing happened, I knew it was a dream. Another big one I use is looking at any words, numbers or clocks to see if they were legit, or random characters / garbage.

I started to "feel" what a lucid dream was because I would get some nightmares that would eventually wake me up. It felt real and I could remember everything about it (for a few minutes). The big ones always involved me falling from a building, and waking up once I hit the pavement.

Over time, I forced myself to try to mostly stay asleep during these nightmares. I remember falling from stuff, hitting the pavement, waking up, but keeping my eyes closed and trying to keep from waking up. It got to the point where I would "half" wake up, but still be in the nightmares. Then with some practice, I could do that to normal dreams too.

I can't really do it on demand, so it's more if I am having a crazy dream, I can usually snap out of it and fully control everything about it.

[basementcat]

+1 on looking at words.

I once was having dinner with a girl and the topic of conversation drifted to dreams and how one might tell if one is in an "Inception" type scenario. I used the menu as an example-- read a line from the menu, close the booklet, reopen and reread the same line. I told her if the two lines aren't the same line, you're dreaming (the rendering hardware in your brain apparently uses different PRNG seeds for procedural texture generation).

I paused awkwardly as I realized that items in the menu kept changing each time I reread them.

She was very offended when I told her she was a figment of my imagination.

[veli_joza]

I like your explanation for changing lines of text, but I don't think brain is actively generating any content. I think brain is just trying its best to apply daytime pattern recognition to un-orchestrated neural activity. The most recently learned patterns are the strongest, which is why often you'll dream stuff that happened that day. If you spend a lot of time performing single activity (like gaming), the dream will be intensive and focused; this is called the Tetris effect.

[logfromblammo]

Poke one finger of one hand into the palm of the other. If you are dreaming, the flesh will yield like putty, and your finger will go through. This also works most of the time with windows, and sometimes with walls.

Pinch your nose, close your mouth, and try to breathe. If you are dreaming, you will be able to inhale and exhale without any conceivable path for the air to flow. Also works if you are underwater.

Light switches always do something in my dreams. It might not be turning the lights on and off, but a thing happens when I flip the switch. (One time, it made some rabbits explode. That was fascinating, and I blew them all up one by one, and then felt guilty about it after I woke up.) Although most of the time, my dreams don't even have light switches, and I don't notice when they are absent from places where they should be, according to building codes.

I almost always have hands and a face, and the ability to move, so the two tricks above usually work.

[nickpsecurity]

"Pinch your nose, close your mouth, and try to breathe. If you are dreaming, you will be able to inhale and exhale without any conceivable path for the air to flow. Also works if you are underwater."

That has happened to me before! It was more an accident of experimenting around in a lucid dream. I didn't think anything further of it. You're right, though, that it should be a default technique since you can close your mouth and attempt to breath in about any dream situation. Thanks a lot!

[kfrzcode]

One day, when you wake up and the power's out you're going to have an existential crisis

[chipuni]

Weird. I've tried the 'flip a light switch on and off' in my dreams -- and the lights do go off and on. Every time.

I use reading and re-reading to test whether I'm in a dream.