Here are my keys for this site. Whenever I bump my Request Thread, I get anywhere between four and ten serious inquiries. I've also stuck with many of my same partners despite my two major hiatuses from the site. So I think I'm doing something right.
1 - Be flexible or be patient. When looking for partners, keep in mind that the more flexible and broad your ideas, the more interest you'll get. The more specific you are the more patient you'll have to be for partners.
2 - Be unique. There are a lot of VERY similar request threads out there. Read through a page of em and you'll see. Make yours unique and you'll get much more interest with much less time and effort.
3 - Read all the way through other people's Request Threads. Nothing will get you a quicker no than asking questions they already answered or asking for things they don't like.
4 - Grammar is the easiest thing you can do right in a roleplay. Don't know how many of my friends on this site have bitched to me about dropping a partner cause they couldn't write a readable sentence. Grammar alone will get you a long way.
5 - Be honest and blunt. Dancing around the point or being too quick to please is how you end up in a roleplay you're not enjoying.
Follow those basic rules and you should have a great time on this site writing whatever your heart desires.
I felt this in my soul.
I'm especially bad at telling people no...
To add my own two cents...Since you specifically asked about reacting to posts/RPs in progress:
1. Read carefully so you make sure to react to everything in a post.
2. Miss something? You can edit posts. Don't be embarrassed. Sometimes you're tired or misread a line. Small misunderstandings shouldn't be the end of the world/story.
3. Keep an open line of communication for OOC questions, comments.
4. Raise concerns right away if something is going in a direction you don't care for. Just because you agreed to a story, doesn't mean you agreed to everything that might happen.
5. Related to above...hash out limits ahead of time, discuss firm NOs so you don't get into tricky territory.
6. Don't let someone pressure you into something you're not comfortable with, but keep an open mind. I have several things that started as a NO and ended up a fave over the years.
7. Discuss post frequency ahead of time. If people know you're going to post once a week v. once a day, it can save some headache.
8. Don't be afraid to tell a partner when it's just not working out. Be nice, and honest.
9. Have fun writing! Grammarly is a nice free add-on that can help pick up spelling errors/grammar issues in the thread post window and let you focus more on content. It's not perfect, but it helps pick up little stuff!
10. BOOP