General
Don't use "would" unless it's specifically relating to a conditional. You will never need to use "would" for future tense.
>He would place his hand against the wall, and stare down the underclassman.
>He placed his hand against the wall, and stared down the underclassman.
If post length is an issue, consider measuring post length in terms of characters, rather than something like "lines".
Don't use "orbs" for eyes. Everybody and their mom does it. "Sex" for genitals is similarly overdone.
If you can, try to use body language rather than outright explaining a character's thoughts. https://imgur.com/gallery/Yz94j
F-List-specific
Make sure that your profile and presentation are the best that they can be, but don't ever believe that your profile is the end-all-be-all. You might find more or less play based on what fetishes you're willing to cater to, or how high or low your standards are. You'll have a far better time if you're not worrying about being popular.
If you're building profiles on F-List, try to have character art that looks consistent. Using images of characters you want to fuck is a good idea exactly 0% of the time.
If you're building profiles for canon characters, don't just copy-and-paste the wikia page for your character. People who want to play with your character will probably have all that information already. Write about your interpretation of the character.
If you don't need a kink to be searchable, you probably don't need to put it on your list. Same applies to sticking more specific kinks in your "no" list when the broader ones would do just fine.
Writing custom kinks? Be specific about how they relate to you or your character. "I like the contrast", as dumb of a phrase as it is, at least clues people into what aspects you like of any given kink. Try to make them interesting to read, though, "I love big tits" won't do you any favors.