Post as much as you want or as little, just dont be a story hog ;)
Be as silly or serious as you want.
Dont be afraid of taking things to new directions :P
Most of all dont worry that you arent very good of a writer, i certainly am not a good writer and i dont expect anyone else to be, not that id know the difference :D

I'll start!

There once was a boy from space, he loved the thought of earth so much, he traveled there. Everything was so odd and exciting...