I've been told there are specific rules to writing different genres. Exactly what are these rules? Ambiguous tenets of adherence to the genre seems to be the answer.
The "Quest" collective should be representative of the fantasy collage. In other words, the group should be made up of humans, dwarves, elves, wizards, etc. Hmm? How can this be a rule? What if the fantasy world is only humans dealing with magic? Could not the collective be made up of different types of humans by occupation? Say, a blacksmith, a farmer and a hunter?
Somebody must die. This is true of mysteries and other genres. But, is it really necessary? Maybe in a mystery but I don't think it is totally necessary. In fantasy, it is not necessary to kill somebody just to get rid of a character. I feel the same could hold true in a mystery. Maybe a dragon eats a character or a person falls into the crocodile pit and is lost, but it is not mandatory to kill a character in any genre. If a death is necessary, the "how" and the "why" are necessary explanations. Because is not an answer.
Sex sells. Perhaps. Some readers want a lot of sex, others prefer a hint or illusion of sex. Only in the last few years have I alluded to sex in my books. Prior to that, my characters were chaste and needed no relationship other than friendship. If Mr. X was in love with Miss Y, only in the finale did the two kiss and that was it! Period. Finito! Today I have learned to be a little more lax and use afterglow to describe a sexual moment. I still refuse to write that explicit sex scene. My rule.
Avoid cliches... with a passion. Not really. If the butler did it, so be it. A writer can pepper the story with a few cliches but don't over do it. Keep it under control. If you, as the author, write "He opened a can of wiggling huckula." We, the reader, know you probably meant worms and if so, you should have said worms rather than throwing some obscure word such as "huckula" at us. The exception would be if you've already described and used "huckula" and we understand it as local fauna to the story. I'd written a story involving cats and was told it was cliche and ho-hum boring. I was advised to spice it up, change the animal to something else. I did, creating a fantastical creature based on an archaeological find and the story was... well, the story was bad. I went back to my original idea, used the cats and the story flowed. My test readers enjoyed the tale and were able to connect with the cats. Cliche worked covering the how, when and why.
One rule I was taught early on was "If a wizard performs magic, there must be some form of exhaustion or expense taken." I don't totally buy into that "law" since if one deals in magic, it is a way of life. BUT, I do support the concept by usually having my wizard needing a rest -- after a MAJOR feat. Lighting a fire, moving an item I see as mundane every day issues but conjuring a dragon into existence is not something done on a whim. Hence a wizard would be exhausted and need a rest. Clapping his hands and moving six people across the continent in a whirlwind, that would be a major feat. Making a love potion would be another mundane request, probably weekly and requiring very little exertion on the wizard's behalf.
Male lead characters must be strong. Female lead characters must be strong. BULL! The lead character can grow and they can experience human emotions. That means they can cry, they can laugh, they can be wrong and they most certainly can accept help. Think about it - Are you at the top of your game every second of every minute of every hour of every day? Wow! How does it feel to be perfect - just perfect? Get over it, the rule that lead characters must lead is a fallacy. Your lead can get lost, need help, hurt, whimper, cry and be bold as the moment calls. In Lord of the Rings, Frodo has moments where he doubts those about him, gets lost, needs help, and most definitely, is scared.
If you've written your story properly, the reader will accept your explanations of the how, when and why of the tale. BUT, you have to KNOW the how, when and why of the story and be willing to support your choice.