Seriously, what is the best way to do it? Is there a right way? To write my screams I use as reference the ones I hear in movies for some realists, and some anime I watch. I don't watch much anime, but I've heard comic screams that I like from there.

But, do screams in text have a place in any dictionary?  Is there a "canon" of how to make a scream for each type of situation? I want to see

Well, there's always the classic comic book options. 

It is very important when writing a novel to use words that you can find in a dictionary when expressing a sound (called onomatopoeia.) 

Boom. Crash. Thud. and of course Ah!

Now to add color to a scream, use adverbs and adjectives, and nouns and verbs that describe both the sound, the reason for the sound, and the end result of the sound.

"AH!" he cried in a blood-curdling way, causing the monster to pee her pants.

That is assuming the monster is a she. And wears pants. And can pee. 😈

I concur with Alexander Harthorne and ArDeeBurger. It's better to stick to onomatopoeias and flavor text, although I don't always follow this advice when it comes to animals and beasts, I wonder what everyone thinks about this, how would you write a wolf's howl? And what about a fantasy beast screams? Would you use a generic 'Roar', or 'Snap' followed by some flavor text or just use a textual description?

EuRoboto Wrote: I concur with Alexander Harthorne and ArDeeBurger. It's better to stick to onomatopoeias and flavor text, although I don't always follow this advice when it comes to animals and beasts, I wonder what everyone thinks about this, how would you write a wolf's howl? And what about a fantasy beast screams? Would you use a generic 'Roar', or 'Snap' followed by some flavor text or just use a textual description?

Well, I would say that, since wolves and beasts and other such oddities don't actually talk, they don't get tagged with dialogue.

The wolf howled. The monster screamed. 
And the pee running down her leg made a warm and golden tinkling sound. 😸

Now that you have some serious answers, I can finally add my own which I waited on.

Q: How to write Screams?
A: You use the following 7 letters "A" "C" "E" "M" "R" "S" "S" in this order "SCREAMS".

IMO, it depends on how much emotional impact you want the scene to have in your story. Parts that don't matter as much emotionally can be cut down. In a battle with one of the villains many disposable henchmen, "he screamed" might just suffice. Worldbuilding and exposition can also be cut in this way, if it suits your writing style. 

In a more emotionally rich scene, then maybe it's better to go for something like "he screamed, his voice hoarse and broken from too many warcries and tasting acrid and tangy of the blood of his vocal cords". Or "as the roller coaster cart dipped over the edge of the hill, he screamed elatedly, screaming out months of stress and tension. Thrill and fear and joy and a sense of freedom, however fleeting, tangented in his voice before, wheezing and laughing, he ran out of air."

Or whatever. But emotionally powerful climax moments can be allowed to have more weight. Let them take up more room. They matter.

EuRoboto Wrote: how would you write a wolf's howl?

EuRoboto Wrote: what about a fantasy beast screams?

Interesting thread. I novelized a screenplay for someone and he spelled out every yell (like in "Eeoooyahh!"). In most novel cases, I simply mention the character screamed. Everyone seems to get that. But screenplays are different because some actor needs to learn those lines. Plus his or her's idea of a scream may not be what the writer had in mind. If I write a movie character giving a battle cry to the hills, I need to spell it out. Otherwise, the actor's going to see "make yell" in the directions and go "Woof".