I know a few tips for that.

* When writing a response, rewrite in your own words the post you're replying to. It shows the other player what you (or your character) thought of the events and improves your readers' immersion.
* Don't describe the environment per se, describe your character's reaction to it. You don't "see a lamp hanging from the celing," you "watch your head so you don't bump into the lamp hanging from the ceiling." There aren't "brambles and thickets around," you "bat away the brambles and thickets."
* Show, don't tell (or don't adverb). You don't "close the book angrily," you "slam the book shut with an ear-splitting pop."