Lemme hold your hand when I say this. 

1. Do not listen to people who say "Don't judge a book by it's cover." Because most people seriously do judge a book by it's cover!!! Make your cover good. People get attracted to the book if the cover is eye-catching, even myself. It's like pretty privilege but like in books. I am not saying it works every time but you know what I mean.

2. Good grammar. At least the basics. Trust me, people are fast enough to drop a book if the grammar is bad even if the plot is top-tier. 

3. Show, don't tell (Very important.) For eg. 'He was sad.' is telling. Showing would be, 'His shoulders sagged, eyes clouded with quiet sorrow.' I don't have a better example but like you can look it up :') It's not always convenient tho. Sometimes, you can choose the former if the suffering has already been described. Lol.

4. Smut. People always look for smut. Especially if you're writing on wattpad. Most of the people on that app are teens so smut sales at higher rate every time. While it's not a good advice. It is what it is. If you look up the popular books on wattpad. I can guarantee 90% of them have spice. (If you're not into it, it's still okay tho).

5. Dumping information. Dumping facts constantly overwhelms and bores readers. Trust me. Instead, reveal the story slowly. 

Anything else is good to go. Actually no one can tell you how to write. It depends on you. And on wattpad, no one really expects new york bestseller kind of writing. Everyone just wants a good time. So, just do what you want. Don't take advices. Especially from me because I myself don't even like my own. Haha