Okay, so this will be highly my opinion and if you don't agree that's fine. This will be about stories I've read, but I'm not pointing out certain ones, that I sort of cringe at as I read it. Also, I'm not talking about grammar mainly because I'm bad at it also. I'm also not saying that I'm good, I'm just going from the perspective of reading.

1. Don't be too fast or too slow
When it comes to reading shipping books, I read a lot of them, and I've come across a lot of these stories that the first meet in the first chapter and the second one they kiss or confess their love to each other. 
That isn't logical, you're going too fast, let them develop their friendship, and if one falls in love with another ,let them think about it and make sure that they are sure they love them and the same the other way around.
Develop your character so that they can blossom a friendship and grow even further, but also don't go too slow. I don't find much of these but I still do. It's like it's visible that they both love each other but they don't confess until chapter 30. That makes readers like me just cringe as their reading it.
Again, this is just my opinion and I'm not talking to anyone in particular, I'm just saying that these are hard to read for me and that this is just constructive criticism.

2. Use paragraphs plz

I know up this sounds a little weird but writing paragraphs shows off more efficient looking writing and can actually affect the story.
If you don't use paragraphs, I'm not saying I hate it, there are actually some people who and amazing and writing and can create a whole background setting in a single well written sentence that don't use paragraphs. All I'm saying is that it makes some readers unable to read it because it bothers them.   
I'm in the middle, I really dont care, but it still affects me a little. This one isn't as prominent as the other one, I'm just making a suggestion.

3. Add stuff to it

When I write, I usually re-read it and add more stuff that will make it more interesting. For example, in my Hamilton modern au, it showed a group chat. Originally I wrote Peggy, or on the group chat, Pegsterlegster, they say shut up.
To add humor and a realistic element to it I decided to add a typing mess up, not auto correct. I didn't add that until I looked back though, and I actually like it a lot more than the just plain 'shut up'.
It's good to add stuff that you didn't realize would be better, it helps you use you mind to make it sound better and more realistic.

Eh that's all for now, I just wanted to share my opinion on writing.

Bye fellow peoples of the world.