This is more list-like in form than the others, but then, it contains some list-like objects and a few pieces of actual advice.
So there.
Advice first.
1) Make sure characters' actions match their motivations as described. If the heroine's greatest ambition is to be free from her mother, it doesn't make much sense that she agrees to an arranged marriage that she suspects will only trap her further under her mother's control. Now, she could have her own reasons for agreeing to it, or she could be planning to break free and run later, or she could see no other choice and plan to react the instant there's an opportunity. But once again, we run into the problem of "Until the author explains, the audience may assume it's a mistake, and if the author never explains, the audience is justified in assuming it's a mistake." If all we hear in the heroine's thoughts is dread about the marriage, why is she agreeing to it?
Sometimes, I feel, fantasy authors don't pay that much attention to their characters' actions at the very beginning of a novel. They give them the goals that will be important towards the end, like the desire for freedom that will lead the heroine to adventuring, and they set up the situation that will ultimately propel the character down the road of change. But they don't put propellers on their characters. They drift along, vague and passive, in the current, and act as they need to for the plot, not as they would be required to by their goals.
The solution to this is either to show why the character is doing these things, hide the reason for now and reveal it later, or have more active heroes. I favor the last solution, personally, since it shows me the author can keep these people in character from the very first moments of the book. If they want grand things and are willing to do grand deeds, I want them to also try to achieve those goals on their own, even if they ultimately can't without help.
2) If a character's actions have to be entirely opaque, try to make sure there are at least the hints of plausible explanations. This is meant more for non-viewpoint characters, while the first one is more for viewpoint characters. Perhaps the about-to-be-married heroine thinks she doesn't need to do anything to resist the marriage, because her brother, who loves her and hates their mother, will rescue her. But when he comes home, he approves of the marriage and advises her to follow through on it. Why?
You could indicate his behavior is abnormal, which might mean magical control by the mother. You could indicate that he's obviously hiding things from his sister; maybe he's in love with the sister of the man she's being assigned to marry, and assumes the wedding will make his own desired wedding easier. Perhaps he talks to her about maturity and responsibility, which could indicate that he sees his own youth in a different light now. And there are half a hundred other things you can do.
What doesn't make sense is for the heroine to expect her brother to rescue her, the brother to show up and not rescue her, and the heroine to immediately continue as if that was just the normal course of things. Come on. She expected this on page 4, on page 50, and on page 63, when she saw her brother for the first time in ten years. Now why does she come out of the conversation with him on page 65 not thinking about his refusal to rescue her at all, or even thinking that there was no way she could have expected his help?
Here, I blame the tendency to have so many mysterious things happening that the author loses track of what ones she hasn't given clues about, combined with the idea that "If I give any clues, it breaks the suspense!" No, dumbass, it breaks the suspense if you don't give any clues and just spring a trap out of the blue later, because suspense does not equal never telling the audience anything. Give clues, if you can't explain right now. The heroine could be dead wrong in how she reasons about her brother's actions, but at least she would be trying to fit them into some sort of order, rather than dropping them like a hot coal because the author wants to concentrate on something else.
Now the list.
3) Money. I do not know why this motivation is treated as the kiss of death by so many authors. Thieves don't desire it if they're heroes; they steal for the sport of it. Good nobles don't want it; they give it away to the poor, and despise anyone who shows off desire for it. Fighter heroes who've slept in the wilderness for ten years don't want it; they sneer at a host who has soft sheets, even as they sleep on them.
Yet, in the real world, many people want money all the time. It's an extremely easy motivation to understand, since it buys so much else. There's not the unrealistic, fluffy-pink tinge that appears when the author tries to make the character too pure an idealist. It's an excellent way to make someone seem practical and hard-headed.
What gives?
Try making one of your characters want things, and see what happens. I'm really enjoying the fantasy I'm reading right now, The Etched City by K. J. Bishop, because one of the heroes, Gwynn, enjoys the good life, kills for money, and isn't punished for it. In fact, the author keeps putting Gwynn in conversations with characters who want to "redeem" him, and letting Gwynn win the arguments. It's marvelous.
Protagonists who want money can work. Don't decide otherwise without trying it.
4) Safety. This might not seem like a workable fantasy hero motivation. You want them to go out and adventure, not be cowards crouching behind walls. But who says characters desiring safety are cowards? If you lock your door at night, are you a coward? If you set off through a war-torn country and try to get to safety with a noble lord who can protect you, are you a coward? It's another sensible motivation, with the added attraction of being harder to get than money in many situations.
The example par excellence here is Martin's Arya. She begins as a nine-year-old girl dreaming of fighting with swords, your ordinary tomboy. Then she actually has to go out and live the life she's been dreaming of. She's in the middle of a civil war. On the other hand, she's nine (ten later). The lengths she goes to to try and find safety, and protect herself on the way there, make her shivery, and creepy, and realistic. A ten-year-old killing, the way that Martin portrays it, is not cool, but extremely sad.
And creepy. Don't forget creepy.
5) Freedom from. Freedom is supposedly the archetypal fantasy hero motivation; they want to go out and wander the roads, free from anybody, free from their parents or their arranged marriages or whatever is making their life "intolerable" back home. (The reason why that's in quotes is coming up). They want to be free to visit the ocean, to fight with swords, to do magic, or whatever. But their dreams are vague, and thanks to a lot of fantasy authors taking extreme delight in making reality nothing like those dreams, they fade and break apart early in the story.
Now, if that's going to happen, the character needs some other reason not to turn around and go right back home. She needs someone or something to get freedom from. The author doesn't do a good enough job in convincing me that her situation at home really is intolerable, so I come to think that freedom isn't the character's motivation. What it often turns into is the character suddenly developing a mania of "I Luv the World!" and continuing in her adventure for idealistic reasons that she swallows whole when they're first explained to her, without question, no matter how much they may contradict what she previously believed.
So give her a defined threat at home. Show me why she's never going back there, even if her dream of becoming a dancer falls through and she turns into a prostitute instead. Show me what's at her back, if you're going to destroy what she thinks is in front of her.
6) Duty. Duty-bound characters are also, supposedly, not really heroic types. They're stolid. They can't do anything. They just do what people tell them to. Rebellious characters who run off and join the army, a la Elizabeth Moon's Paksennarion, are much more interesting.
This is because authors don't think themselves deeply enough into the minds of duty-bound characters, or haven't seen enough good examples to know what they look like. Yet there are good examples out there, two of which I will mention in a moment. And I prefer both of them to characters snapping out in yet another ill-tempered "rebellion," particularly when the author, as in point 5, has not made their home situation seem all that difficult.
Pratchett's Vimes is, I would argue, duty-bound. He has to obey orders from the Patrician. He protects the city of Ankh-Morpork, not a prophecy or a sword or a small group of persecuted people in a hidden valley. He's a policeman, for fuck's sake. Though he does things that aren't always legal, his motivation is duty, and justice, and love of the city. He doesn't run away from everything just because people expect things of him. And he's one of the more interesting characters I've ever read, more interesting than a dozen tomboy rebels.
On the terrifying side, Martin's Stannis Baraetheon is absolutely committed to justice, and what he sees as the rightful rule of the rightful king (that would be him). He will do anything, including some things that he states are repugnant, in order to fulfill justice. And he really does come across as someone who wants the throne because he thinks he's the only one, by right of bloodline and claim, fit to sit on it, not someone who is taking the throne because he really wants to rule and abuse people.
7) Stasis. Supposedly, the desire to change everything is more powerful than the desire for stasis. I don't agree. It depends on the situation.
One problem I have with some fantasy rebels is the nebulosity of their dreams. They're going to change the whole country for the sake of some golden age that they can't define? Okey-dokey, then. It could certainly happen- it's happened all the time in our own history, that people start agitating for the sake of love! and justice! without knowing what love or justice would look like- but the narrative often doesn't doubt or question the rebels' actions, or the cost of their rebellion. Rebels are the guaranteed good guys, 90% of the time. The author is behind them 100%. If people on the bad side, or the peasants, die, oh well. And then the book ends when the rebels win, so we don't get to see what their actual concrete goals look like at all.
Against this, put people who want things to stay the same, because the status quo is comfortable, or for religious reasons, or because "this is the way we've always done it." They, in contrast to the nebulous rebels, know exactly what their goals look like; their goals are sitting here in front of them. And while things might improve if their lives change, they can't know that. So they cling to the present with all their might.
The force of inertia is a damn mighty one. Try putting a protagonist on the side of the status quo, and it should be immediately obvious what he wants, and why he's not going anywhere if he can help it. It might still be wrong, but it's not automatically silly to present someone as standing in opposition to a rebellion. Look how quickly rebellions often collapse.
8) Sex. This is another one that motivates some fantasy heroes, but only in nebulous form. Quite often, it's not sex, it's love. They want to get together with their one true love, and it's implied that, yes, they'll have sex, but the author focuses on babies and companionship and a sense of belonging. It's the villains who want sex for its own sake, who feel lust, and who are often evil because of it.
Yet it makes a perfectly acceptable motivation for anyone, I think. And people will go to extraordinary lengths, even risking life and limb, to get their jollies. If that character's particular jolly is declared illegal, or dangerous, or blasphemous, or whatever, he might stumble headlong into trouble trying to get it.
Raule, the main female character (I can't call her "heroine," knowing what that word often implies about sex) of The Etched City, is, at the point in the book I'm at, having an affair with a boy half her age, because she wants to. She considers the moral implications, and decides that she doesn't care. It's one among her several motivations, but it does keep taking her back to a lover who's a thief and likely to die of violence At Any Moment Now. Not the wisest choice if she wants eternal companionship, but the author doesn't imply that; it's sex, and not love, that keeps the affair going.
That list isn't exhaustive by any means, but I tried to bring up some that I don't think get as common a hearing as revenge, love, or the desire to save the world.