Now, how to create a good plot or storyline.
Brainstorm. Manipulate. Work.
If a plot comes to your mind, jot down the highlights but don't act on it immediately. Juggle the plot in your head. Weigh different scenarios and situations. Add twists and unimaginable things.
Once you are sure that you have reached the absolute perfect version of the raw idea, work on it.
Basically, write the whole book in your head.
If you start acting upon your ideas in spur of moment, you'll most likely end up bored with it or with a writer's block.
The plot for 'My life as a trouble magnet' was inside my head for at least 4-5 months until I wrote the first chapter.
If a chapter, paragraph or line is not satiating you, then it will definitely not satisfy your readers. Re write it, reimagine it and carve it to perfection (whatever the definition of perfection for you is)
Try to write in a way that the reader loses the sense of reality i.e. they get so engrossed in it that they start feeling the emotions of your characters.
Do not stretch something for too long. If the time is good, do not stretch all happy for too long and vise-versa.
Do not repeat a situation. Like in some books, I notice how making up and breaking up keeps on repeating in a cycle. The characters will get close and then most probably the boy will do something and they go back to hating each other until something happens and they come close again.
This is plain boring.
If your book is under Humor, do not limit it to humor. Life is never given to us with genre. Sprinkle all sorts of moments from action, adventure, horror etc. This will make it unique and spark the interests.
Always, write in a way that leaves your readers wanting for more. It's not always about cliffhanger, sometimes a little amount of mysterious hints here and there are enough too. But make sure that there is something that brings them back in order to satiate their curiosity.
Try to be grammatically correct because let's just admit it, there are a truck load of grammar nazis here who would point out 'Humour' instead of 'Humor' but won't notice that I AM NOT FREAKING AMERICAN!
Especially for people who don't speak english as first tongue (like me), you'll have to work harder on that. (I try but even my work has typos sometimes) Proof read your work and don't get disheartened if you manage to let a few typos slip even after that. Even famous writers need editors, we're diamonds in rough in front of them.
Try not to be monotonous. If you're describing a dress, do not waste 3 pages on it. Nobody gives a damn, simply add the picture of dress. Half of the books that I abandon in middle are abandoned because I get completely bored of excessive explanation or straight drive. Life is a rollercoaster and your book should take inspiration from it.
If you're describing love, do not- I repeat- do not abandon the best friend. She used to be your lead's everything at some point. Do not center the plot around a specific group out of cast (especially the couple in spotlight). This is not how world works in reality. No matter how obsessed you are with a person, you don't spend every second with them or thinking about them.
Do not rush your plot. I read a few books where the author literally didn't describe anything. The plot will go like-
'She stole my date and I was angry but then warren asked me out and I didn't mind until she called me upstairs and we fought. She ended up jumping off the roof and eventually died.'
DUDE HOW THE CAN YOU DESCRIBE THEFT OF YOUR DATE, NEW DATE, FIGHT, SUICIDE AND DEATH IN TWO DAMN LINES?!
(I have read a book with lines like that. I am not making it up.)
You've to maintain a balance. Not too much depth and not too much rush.