Are you dreaming right now? This is a tricky answer to get correct, ever since Albert Einstein showed this ``now'' concept was too complicated to work with. He might even point out that ``you'' is a pretty insufferably vague concept that's too proud of itself. When an amusement park notice warns ``You must be taller than this ride to sign this sign'', who is being referred to, unless that should be whom, and in any case are you? Yhoum? Only the ``the'' makes good sense and it's not even in the question.
It's a question worth having a ready, and even more worth having a correct, answer for since you might win a call-in giveaway. And there's the practical application. Suppose that years after leaving school you find yourself back in high school, forced to answer silly questions about the ``Wilmot Proviso'' in mathematics class or the herpolhode in gym. If you're certain you're dreaming you don't have to worry that you have anything wrong except for the question of whether you are dreaming. If you're not dreaming then you've travelled backwards in time and risk messing up all of history since that date, possibly including spoiling the Voyager 2 encounter with Neptune.
So it's important to remember things such as the number of your high school teachers who were forty feet tall and had dozens of tentacles but good chalkboard habits. If the number you see is incorrect you are either dreaming or have substitutes and can arrange your strategies appropriately. If you don't remember which of your teachers were extraterrestrials write to your school immediately and ask them. After all this time they're probably glad to give you the answer, once you pay the outstanding $1.85 library fine. Keep the answer in a warm, dry spot for at least 45 minutes until a toothpick in the center comes out.
Yet there are nearly eight officially licensed dreams that people may have, and telling whether one is in them can depend on noticing odd or incongruous elements. For example, suppose you wake up to find that author Jonathan Lethem is in your bed. By itself this suggests you are dreaming. But then what if you are author Jonathen Lethem? Then to be confident you were dreaming you should have to find author Michael Chabon in your bed instead. But how to tell in the confused state of not knowing whether any authors should be in your bed? The simple answer is to write down a quick note on a highly visible body part which reads `NOT AUTHOR JONATHAN LETHEM' (though author Jonathan Lethem should write one fewer or one more `not'). This will not always help: you might fall out of bed instead. Sometimes you have to think on your feet, so try standing up.
Another way to tell you aren't dreaming would be to carry around a book of crossword puzzle solutions, on the theory your sleeping mind could not possibly instantly work up such a large grid of letters so highly organized, what with the trouble you have while conscious finding an eight-letter word for `governor' that isn't `governor' all over again. As there just can't possibly be one, if you find it in your solved puzzles then you know you're dreaming.
There can be other subtle clues to whether an experience is a dream or reality. For example if you find you're sharing an apartment with eight strangers in the only building on a block reaching from horizon to horizon in Albany, New York, adjacent to a municipal airport-sized parking lot, with a loud parade perpetually over the horizon, then you can be confident this is real, since no one has dreams about living in a geographically inaccurate representation of Albany, New York. But be careful: if you are sure this is nearby Cohoes, Rensselaer, or Loudonville, you will spend much of your life explaining to people who don't come from there how to spell or pronounce the place's name.
If your high school doesn't get back to you with the extraterrestrial teacher count, it was most likely three, and they are probably hiding something. Try not to sleep through it.
Trivia: The United States Signal Service instituted a uniform definition of thunderstorms for its weather observers in 1884. From that time, if observers could hear thunder clearly, it could be called a thunderstorm, even if there were no rain. Source: A History of the United States Weather Bureau, Donald R Whitnah.
Currently Reading: The Speckled Monster: A Historical Tale Of Battling The Smallpox Epidemic, Jennifer Lee Carrell.