In the UK there is a TV quiz show called
Only Connect. It is all about finding connections between apparently disparate things.
The easiest questions are those where there is only one answer that could work. For instance:
1 - Kennilworthy Whisp
2 - Newt Scamander
3 - Robert Galbraith
4 - JK Rowling
Answer - JK Rowling has published books under all four names.
Where it gets really hard is the middle of the show. They give you 16 different answers in a grid, which form four groups like the one above. What's especially tricky is that many of the answers could go into more than one group. (This is the "Wall" round, and you can play them online here:
http://www.bbc.co.uk/programmes/articles/2Z79DzzJY8w2R58bpftq14k/quiz).
That's how you make great clues - find things that could be a dozen different things, all equally valid.
I wanted to add something about red herrings and twists here, because I forgot to in my earlier posts. I occasionally see a misconception (usually from people unfamiliar with the MTS genre) that red herrings and twists are random things thrown in to keep the reader guessing until the end. I disagree.
Let's start with twists. Using the
Only Connect four-clue structure again:
Clue 1 is "Michelangelo". First thought is a painter, but it could be
half a dozen other things .
Clue 2 is "Leonardo". Looking more and more likely to be painters, specifically renaissance painters.
Clue 3 is "Donatello". By this point, painters seems to be utterly certain.
Then clue 4 is revealed: "Splinter". This is the twist.
Turns out it was Teenage Mutant Ninja Turtles all along! The twist doesn't invalidate the original clues - it just puts them in a different light. They still make sense, but now they make a different sense when considered with the twist (note, for instance, that it's just "Leonardo" and not "Leonardo da Vinci" as usually written). Importantly, the twist is a valid and key part of the set of clues - it's not just something random thrown in there.
Now, the same sequence with a red herring:
1 - Michelangelo
2 - Leonardo
A - Copernicus
3 - Donatello
4 - Splinter
In the context of 1, 2, and A, you might think, "A-ha! it's not painters, it's renaissance polymaths! That was a clever trick." (Or, you might not, and in the case of fiction, it may take quite a lot of detective work for the main character to be able to make this conclusion.)
But then when given clue 3, it doesn't make sense. You have to disregard it - and once you have clue 4, you can see that it doesn't fit at all with the rest of the set.
You can go further, if you want, and include more than one red herring:
1 - Michelangelo
2 - Leonardo
A - Copernicus
3 - Donatello
B - Galileo
C - Kepler
D - Huygens
4 - Splinter
By the time you get to clue B, you're thinking - "right, it is polymaths, and 3 (Donatello) is the red herring. I should disregard it."
But then you get C, and then D. The polymath thing stops working. Sure, these are famously intelligent people. But the connection isn't holding together as it should.
There are two ways this could end. The first is that you realise that clues A-D aren't part of the main set. You think that it goes:
1, 2, 3 - painters
A, B, C, D - 17th Century astronomers
Then, as in the first example, you get clue 4 and realise the first set is actually Teenage Mutant Ninja Turtles (the twist).
OR
You get clue 4, and only then do you realise that the two sets are
1, 2, 3, 4 - Teenage Mutant Ninja Turtles
A, B, C, D - 17th Century astronomers
The difference is that here, the twist actually manages to provide the answer to both sets of clues, by making it clear just what you're looking at with the "main" set.
This structure, with lots of red herrings, is actually a subplot when you think about it. For me, these are the most satisfying kind of subplot: they closely intertwine with the main plot, but they have their own resolution and internal logic - it's just that that logic doesn't become clear until you realise they're not the same thing as the main plot.
The two "endings" given above are both ways of resolving that subplot. The first allows you to "clear the board" and focus on the main mystery. This is useful in thriller-type plots. The second keeps all the cards in play until the final clue, which is great in a straight mystery but could be confusing if you don't handle it right.
There is a virtually unlimited number of plots you can create using these elements. Think about having more than one twist - say there was a clue 5 that totally transformed things all over again, just like clue 4 did above. Or try having multiple sets of red herrings, where a third set of clues might complete sets 1 and 2 equally.
Just make sure you don't confuse yourself too much...