When it comes to screenwriting, it's important to set the tone directed towards your genre, whether it's a comedy, a drama, a thriller, and so on. It's important to know that no matter what genre you're writing, the story is going to be the most important part of your script and the other elements of your genre can come later.
Comedy
There are a variety of ways you can apply comedy to your genre. Most comedy films usually have some humorous lines and other comedies have slapstick comedy in their films. Other times, there the story as a whole can set the tone of the film based on the premise alone. For example, The 40 Year Old Virgin contains humorous jokes and some comedic moments where something painful happens to the protagonist and we laugh at it because it's funny. Other times there are jokes that are used in dialogue and we tend to laugh a few times in each scene. So when you're writing your script, don't worry too much about the jokes and focus on the story. Not every scene has to be humorous, but there still needs to be conflict and needs to serve a purpose in the film.
Drama
As the genre suggests, dramas are supposed to be serious and sad. Unlike comedies, dramas have some suspense and have a dark tone to it. When you're writing a drama, it's important to make sure the tone is mellow and let the suspense build until the end of act 2. Your goal in this case is to make sure Act 2 ends with something that destroys your protagonist internally. For example, maybe someone close to them died. Once you have that emotional scene, you can spend your third act with a calm mellow tone and show the events of what happens after. How does the character change?
Thriller/Horror
Everyone likes to be scared right? Okay, maybe not me. When you're writing a horror/thriller, it's important, once again to not worry about the jump scares and instead, create suspense and tension in your script. You always want to keep your audience on the edge of their seat wondering what's going to happen next. There are some horror films that have scenes where you might think a jump scare is going to happen, but it turns out it doesn't happen. The tone of the film shouldn't make the audience feel calm throughout because it's boring if there's no suspense. Remember, focus on the story you're telling and worry about the scary parts later.
Of course, you can do a mix of genres, just as long as you are able to set the tone of the film. If you need any assistance with setting the tone of your film, feel free to reach out to me and I'd be more than happy to help you out.